Porous Pavement for Water Quality and Quantity Management

ABSTRACT

A sorptive-filtration system for removing at least one of negatively or positively charged ions, complexes or particulates from an aqueous stream. The system includes a) flow formed substantially from at least one of rainfall-runoff or snowmelt-runoff; b) a filter containment communicating with the runoff stream such that at least part of the stream passes through the filter containment; and c) a granular filter media disposed within the filter containment, the filter media having an amphoteric material applied thereto, wherein the amphoteric material comprises a metal selected from at least one of Fe, Al, Mn, or Si.

This application is a continuation-in-part of Ser. No. 10/842,328, filedMay 10, 2004, which is a divisional of Ser. No. 09/916,171, filed onJul. 26, 2001, which is a divisional application of Ser. No. 09/714,366,filed on Nov. 16, 2000. This application is also a continuation-in-partof serial number PCT/US04/28342 filed Sep. 1, 2004 and this applicationincorporates by reference all above applications in their entirety.

BACKGROUND OF INVENTION

1. Technical Field

The present invention relates to the removal of cationic, anionic,complexed or particulate contaminants from liquids and gases. Inparticular, certain embodiments relate to particle clarification andsorptive-filtration by media which removes chemical constituents andparticulates in a liquid or gas passed through the media.

2. Background Art

An area of increasing concern in the environmental sciences andengineering, particularly process control is the treatment or control ofspecies that represent an environmental, ecological, human or processconcern. Common examples include metal species and phases such as formetal elements Cd, Cu, Zn, Ni, Pb, As, Ag, V, and Cr, as well asnon-metal species and phases such as for constituents phosphorus andnitrogen species which become water borne and are carried by urban andrural rainfall-runoff and snow-snowmelt (herein identified as “runoff”)to drainage systems (herein identified as “drainage”) receiving waters,water supplies, and to natural and anthropogenic terrestrial interfacessuch as soils, the subsurface or earthen deposits. As used herein, ionsor complexes being “water borne” means being transported in water in anymanner, whether the ionic or complexed form is in solution, as aprecipitate material, or is transported by water through a particulatebond or physical-chemical or biological attachment to a particle, in theform of a surface complex or a colloidal bond, or carried by theadvective or diffusive transfer of water. Common manners in which suchspecies and phases become water borne is through leaching, dissolutionor particulate-bound entrainment by runoff from surfaces of the built orconstructed environment, for example paved surfaces, or from humanactivities such as industry, manufacturing and agriculture. Thesespecies and phases are typically deposited on urban surfaces such asconstructed surface, open surfaces, soil surfaces, and paved surfacesthough vehicle exhaust, fluid leakage, vehicular wear, pavementdegradation, particulate deposition, litter, illicit discharges,downspout discharges and pavement maintenance. These species and phasesare typically deposited on earthen or soil surfaces through agriculturalprocesses such as fertilization, pesticide application, insecticideapplication, and soil amending and land-disturbing practices such asearthwork, grading, cut/fill excavation and surficial as well as deepsoil modifications. Subsequent hydrologic precipitation results in themass transfer of these species or phases either in ionic, complexed orparticulate-bound forms and transports these species and phases insurface or subsurface flows by advective, diffusive, gravitational,chemical or electromagnetic gradients.

The particulate and colloidal matter (herein identified as“particulates) itself can be deleterious, representing an environmental,ecological, human or process concern that requires control. In thisapplication, “particulate-bound” means any bond, precipitate or complexassociated with particulate material that ranges in size from colloidal(<1 μm) to suspended (1-˜25 μm) to settleable (˜25-˜75 μm) to sediment(˜75 to 4750 μm) larger gross solids or debris (>75 μm) or floatablematerial. While the size limits of each class of particulate matter areapproximate because of properties such as specific gravity and geometry,taken in total these classes represent the entire size gradation foundin surface runoff, drainage or subsurface flow. The ionic fractions canbe quite variable. For example, metals such as Zn in certain source areaurban watershed locations under conditions of acid rain can be greaterthan 80% dissolved (f_(d)=0.8); while in other watershed or in lowerlocations of the same watershed, the f_(d) for Zn can be as low as 0.2.The remaining percentage is largely particulate-bound but may be acomplexed aqueous species. However, in the simplest two-phase model ifthe dissolved fraction is 0.8 then the particulate fraction for Zn is0.2. This 0.2 will then distribute across the particulate size gradationas a function particle indices such as surface charge, surface area,mass and number gradation, composition of particle and contact time.

It is desirable to intercept the runoff or drainage and remove thesespecies, phases or particulates prior to allowing the water to continueto drainage areas, water supply areas, through the subsurface or in adown-gradient transport to a sea or ocean. One method of separating thewater borne species whether in dissolved ionic, complexed, precipitateor particulate-bound forms is to pass the water through a media ormedium that functions to provide a range of mechanisms from surfacecomplexation, ion exchange, adsorption, absorption or precipitation(herein collectively; identified as “sorption”) and also provides arange of mechanisms such as interception, sedimentation, impaction,straining, adhesion or physical-chemical-biological sorption ofparticulate matter (herein collectively identified as “filtration”).Such a media or medium is identified as providing sorptive-filtration.

One of the most common media for removing particulate bound metals fromwater is sand and sometimes perlite. However, sand has very littlecapacity for removal of dissolved or complexed species and therefore, isgenerally not considered effective in removing these species. A commonmedia used for drinking water is granular activated carbon (GAC) and haslong used as a media for removing dissolved organic species and alsobeen used for species such as metals. However, for many cationic speciesGAC has relatively little sorptive capacity and rapid breakthroughoccurs and thus, sorbed metals must frequently be removed or the GAC“recharged.” Also, GAC has low compressive strength and cannot supportvertical, lateral or shear loads. Any application which places suchloads on the GAC material may cause crushing, significant deformationand a greatly reduce sorptive-filtration capacity and impair physicalcharacteristics of the GAC and the sorptive-filtration system. Similarlyearthen materials such as natural perlite or modified perlite have beenused for filtration and/or sorption. However perlite itself also haslower strength and loading characteristics and lower sorptive capacityfor many metals and non-metals such as phosphorus.

A much more recently developed sorbent media is iron oxide coated sand(IOCS). IOCS is formed by coating silica sand with a thin layer of ironoxide and it has been shown to be an effective sorbent media forcationic species such as metals or anionic species such as phosphorus,in part dependent on the pH and point of zero charge (pzc) of thesurface coating. Iron oxides and hydroxides possess little or nopermanent surface charge, but will take on a positive or negativesurface charge in the presence of protons or hydroxyl ions. In otherwords, depending on the pH of the solution in which the iron oxide isplace, the iron oxide may take on a net positive or negative charge. Asubstance which exhibits a net positive or negative charge depending onthe pH level may be referred to as an “amphoteric” substance.

Iron oxide typically has a smaller net charge (either positive ornegative) in a pH range of approximately 7 to 8. When the pH rises aboveapproximately 8, the iron oxide becomes more negatively charged. Thus,positively charged cations will engage in a sorption reaction with theiron oxide surface or suspended/colloidal particulates with or withoutbound metal or non-metal species and borne by water passing over thenegatively charged iron oxide will tend to bond to the iron oxide and befiltered from the water. Conversely, if the pH falls below approximately7, the iron oxide becomes positively charged and is less likely to bondwith cationic species, but will bond with anionic species or complexes.The pH at which the net surface charge of a particle is zero isdenominated the point of zero charge or “pzc”.

One major disadvantage of IOCS, coated on an unprepared substratesurface is that the oxide coating is not sufficiently durable. Forexample, the comparatively smooth surface of sand particles tends toresult in the oxide coating flaking off. Attempts to avoid this flakinghave led to time consuming sand preparation efforts such as cleaning thesand of organics or weak surface coatings and applying a scratch surfaceto the sand before applying the oxide coating. However, even with thesepreparation efforts, IOCS still exhibits flaking and thus a reduction inoxide coating durability. The smooth surface of the sand is alsodisadvantageous from the standpoint of providing a comparatively lowspecific surface area (SSA) for bonding. The specific surface area of amaterial is generally defined as the surface area per unit mass with thetypical unit being m²/gm. As used herein, specific surface area meansthe total area on the surface of the material in addition to anyavailable porous internal surface area (such as for the GAC discussedabove). The greater the surface area of the substrate, the greater thesurface area of oxide coating that will be exposed to water bornemetals. Thus, it is desirable to provide a substrate with a relativelylarge SSA not withstanding other design constraints. For example the SSAof rounded silica sand is approximately 0.05 to 0.1 m²/gm.

Another problem found with IOCS is the tendency of the oxide coating tocrystallize. When the coating crystallizes, the crystals set up amorphology which does not result in the highest surface area of thecoating. The surface area of the coating is much more optimal if theoxide molecules are randomly distributed in a non-lattice or “amorphous”fashion. For example, the SSA of IOCS may approach 85 m²/gm if a methodof sufficiently inhibiting crystallization could be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an upflow filter.

FIG. 2 is a chart of surface charge versus pH for certain amphotericcompounds.

FIG. 3 is a chart of aggregate distribution.

FIG. 4 is a cross-section of a roadway.

FIG. 5A is a filter system having multiple layers of differentamphoteric media positioned therein.

FIG. 5B is a filter system formed of a fixed matrix media having twodifferent layers of amphoteric material.

FIG. 5C is a filter system having a containment of media in a filterhousing.

FIGS. 6A and 6B are different views of an alternative filter systemhaving a containment of media in a filter housing.

FIGS. 7A and 7B are filter systems having media containments positionedon down spout drains or similar types of drains.

FIGS. 8A-8C are filters illustrating different manners of containing agranular media.

DETAILED DESCRIPTION OF THE INVENTION

The filtering media or medium of the present invention generallycomprises a sorptive-filtration media or medium. The term “filter media”or “media” means any substrate used for filtration whether in the formof granular particles, a fixed porous matrix, or any other form whichmay accomplish the objects described in this application. The mediamaybe sorptive in that it may include a substrate with an amphotericsubstance or compound applied to, coated upon, or bonded to thesubstrate to produce a high specific surface area media capable ofsorbing (i.e. the physico-chemical capture of) dissolved, ionic,complexed or particulate-bound contaminants or particles. The media mayalso have a filtration characteristic which relies on the physical (orphysical-chemical) capture of contaminants which are larger than thespecific openings in the pore spaces in the media or medium.

In one embodiment, the liquid (or gas) to be treated will be passedthrough a granular or a fixed medium incorporated as part of a unitoperation and process (UOP) or as a separate UOP that forms part of atreatment or modification system for liquids (or gases). In particular,certain embodiments relate to removal of metal species and phosphorusspecies either in aqueous ionic forms, as aqueous complexes, asparticulate-bound or colloidal-bound species; and as precipitates.

In another general embodiment, the invention includes a granularsubstrate with an amphoteric substance applied thereto in the presenceof a crystal inhibiting agent (for select substances or combination ofamphoteric substances the explicit or additional use of a crystalinhibiting agent is not required). The granular substrate could be sandor any other granular substrate such as crushed limestone, crushedconcrete, or other granular substrates such as polymeric beads (or othershapes), natural substances, or modified substances such as perlite. Inanother general embodiment, the present invention includes allsubstrates having a specific surface area of 0.1 m²/gm or greater andhaving an amphoteric substance applied to the substrate. In these latterembodiments with a substrate having an SSA of greater than 0.1 m²/gm,the substrate could include a wide variety of materials such as precastcementitious porous pavement (CPP) discussed herein (one form of whichhaving an SSA of 5-10 m²/gm), wood chips, recycled concrete chips,recycled concrete pavement rubble, fired clay or silt material, cementedclays or silts, perlite, zeolites, natural aggregates, syntheticaggregates, polymeric compounds, granular activated carbon (one form ofwhich having an SSA of 600-1300 m²/gm) etc. The amphoteric substance ofthe present invention is intended to include any substance or compoundhaving amphoteric properties or which exhibit amphoteric properties whenin an aqueous environment. Certain embodiments of the amphotericsubstance include compounds such as oxides of iron, manganese, aluminum,or silicon. Certain non-limiting examples of amphoteric substances, e.g.for iron, include the more common mineral forms identified in table 1,or the various mineral forms of manganese, aluminum, silicon orcombinations thereof of these four. Non-limiting examples of manganeseforms may include Pyrolusite, Ramsdellite, Nsutite, Hollandite,Cryptomelane, Coronadite, Romanechite, Todorokite, Birnessite,Vernadite, Rancieite, Buserite, Lithiophorite, Manganite, Hausmannite.Aluminum is typically listed as classes of aluminum oxides, hydroxidesand orthohydroxides (although there are many polymorphs for aluminum).Some common mineral forms are gibbsite, bayerite, boehmite, anddiaspore. Some forms of silicon are silica, quartz, cristobalite,tridymite, and opal.

In some embodiments, an amphoteric solution is formed by dissolving asalt of iron, manganese, aluminum, or silicon (or any combination ofthese) in a solute. The substrate is then exposed to this solution byimmersing, spraying, or other application. The liquid is volatized in adrying process to leave behind a metal oxide bonded to the substrate.Typically any remaining component of the metal salt (e.g., nitrate,sulfate, or chloride) is readily washed off the substrate leavingpredominantly the metal oxide. Although in many embodiments theamphoteric substance will be at least one oxide of either Al, Mn, Fe, orSi, the amphoteric substance may include other combinations of forms ofAl, Mn, Fe, or Si which exhibit similar amphoteric properties whenapplied to the substrate, regardless of the manner of application.

In regards to iron oxide compounds, there are at least 13 iron oxideminerals, of which there are 8 major iron oxides. These iron oxidesdiffer in composition, the valence state of Fe and in crystallinestructure. However, all iron oxides contain Fe and O or OH. Table 1summarizes the major iron oxides with selected characteristics.

TABLE 1 Selected properties and attributes of major iron oxide minerals.Mineral Structural Density SSA Name Formula system (g/cm³) (m²/g) ColorHematite α-Fe₂O₃ Trigonal 5.26 20-30 blood red Maghemite γ-Fe₂O₃ Cubicor tetragonal 4.87  80-130 Chocolate Magnetite Fe₃O₄ Cubic 5.18  ~4black Goethite α-FeOOH Orthorhombic 4.26 20-40 mustard Lepidocrociteγ-FeOOH Orthorhombic 4.09 70-80 Orange- brown Ferrihydrite¹ 5Fe₂O₃•9H₂O²Trigonal 3.96 180-300 deep brown Feroxyhyte δ′-FeOOH Hexagonal 4.20190-210 Brown Akaganeite β-FeOOH Tetragonal 3.56 ~30 dark mustard¹ferrihydrite & feroxyhyte have the only amorphous or poorly-crystallinestructures low SSA from Fe(NO₃)₃9H₂O hydrolysis, high SSA from Fe³⁺precipitation with KOH ²other formulas include: Fe₅HO₈•4H₂O andFe₆(O₄H₃)₃ point of zero charge (pzc) for all minerals shown is betweenpH 7-8 α: hexagonal close packed (more stable than γ) β: goethitepolymorph in presence of high Cl⁻ levels γ: cubic close packed δ′:poorly-ordered ferromagnetic form of FeOOH

From Table 1 it can be seen that the more amorphous ferrihydrite orferoxyhyte are the forms of iron oxide with the highest SSA. If theseforms are coated onto silica sand, their higher SSA, as compared to saythe more crystalline hematite, will create a more preferable sorbentmedia. For this reason, a one embodiment of the amphoteric compoundfocuses on the use of these forms, specifically ferrihydrite. Thoseskilled in the art will understand that ferrihydrite is not produced inisolation, but is typically formed in a solution having various otheriron oxide compounds. The ferrihydrite may transform into other, morecrystalline iron oxide compounds (such as hematite or goethite)depending on factors such as temperature, pH, and whether the ironsource is ferric or ferrous ions. To inhibit such transformation to themore crystalline compounds, inhibiting agents such as silica (SiO₂),silica fume or silica gel, inorganic compounds such as phosphates,polymeric compounds whether naturally occurring (e.g. natural organicmatter in soil) or synthetic (e.g. polyethylene), sodium hydroxide,oils, grease, or any other substance which inhibits crystallization, maybe introduced in certain embodiments of the process for synthesizingferrihydrite or applying the iron oxide coating. In certain embodimentswhere sand is the substrate, a highly acidic compound, such as ferricnitrate or ferric chloride (used to form the amphoteric compound asdescribed below) may dissolve silica off the sand substrate, therebyproducing an inhibiting agent. Because so many substances may act asinhibiting agents, it is possible that certain impurities in thematerials selected (such as grease or oil in a sand substrate) can beengineered to act as a sufficient inhibiting agent without the additionof further inhibiting agents. While typically advantageous to use aninhibiting compound with iron oxides, it may not be necessary when theamphoteric compound is an oxide of manganese, aluminum, or silicon.However, the use of an inhibiting agent with the latter compounds iswithin the scope of the present invention.

Two known methods for producing ferrihydrite follow. The first methodinvolves preheating 2000 mL of DI water to 75° C. in an oven and thenwithdrawing the water and adding 20 g of unhydrolyzed crystals ofFe(NO₃)₃.9H₂O. The solution is stirred rapidly and reheated at 75° C.for 10 to 12 minutes. The formation of iron hydroxy polymers will changethe solution from a dull gold color to dark reddish brown. The solutionis then dialyzed for three days to produce approximately 5 g offerrihydrite. This procedure produces a ferrihydrite of lower SSA, inthe range of 180 to 200 m²/g.

A second method involves dissolution of 40 g of Fe(NO₃)₃.9H₂O in 500 mLof DI water and addition of approximately 330 mL of 1M KOH until the pHis 7 to 8 while stiffing the solution. This procedure produces aferrihydrite of higher SSA, in the range of 200 to 300 m²/g. Thesolution is then centrifuged and dialyzed to produce approximately 10 gof ferrihydrite. While both of these procedures work well for a smallmass of ferrihydrite (i.e. 10 g) in a laboratory environment, they arenot easily adapted to be economically feasible at production or fieldscale levels that require tons of such a coating. Rather, the abovemethods would require design and construction of a plant-sized processto produce multiple tons of ferrihydrite.

Another embodiment of the present invention includes another, moreeconomical method for producing sufficient quantities of ferrihydrite.In this method, the source of ferric ions is either Fe(NO₃)₃.9H₂O,(ferric nitrate (FN)) or FeCl₃, (ferric chloride (FC)). Both FN and FCare available as reagent-grade salts or available commercially in largerquantities as bulk solutions. FC has the additional advantage of beingmore economical and being a by-product of pickling waste. When FN or FCare dissolved in potable water to produce an approximately 1M toapproximately 3M solution, the resulting iron oxides in the solutionwill typically be approximately 50% ferrihydrite and 50% other ironoxides.

One substrate to which a coating of amphoteric compound may be adheredis sand. Sand typically has a comparatively low SSA of about 0.05 toabout 0.10 m²/gm. Moreover, this low SSA is indicative of a relativelysmooth surface to which iron oxide coatings will have difficultyadhering. As discussed above, without some agent to inhibitcrystallization of the iron oxide coating, the SSA may remain in therange of 1 to 5 m²/gm. Two examples of producing a sand substratefiltration media with a markedly improved SSA (about 5-20 m²/gm) bysubjecting conventional sand to a multi-step process are as follows.

In the first example, the sand was first cleaned and tumbled in acidicsolution (of a pH<2), rinsed with DI water, and then cleaned and tumbledin a very dilute basic solution before a final rinse is made. Second, topromote bonding, an initial scratch coat applied by immersing the sandin an approximately 1M FN solution. The sand was then heat at about 100degrees C. until this coating was dry and then the sand wasdisaggregated and rinsed in DI water to remove any loose coating. Afterthis rinsing, the sand was reheated until dry and then cooled. Third,the sand was immersed in another solution of 1.6 M FN. In this solution,1,000 ppm SiO₂ was added (in the range of 1% of the aqueous volume) tohelp inhibit the transformation of ferrihydrite to hematite or possiblyto goethite. Fourth, the sand was again dried with drying timesminimized in order not to promote the transformation to hematite due todehydration. However, drying of the sand at high temperatures could alsolead to thermal transformation of ferrihydrite to hematite. It wasdetermined that drying could take place at an acceptably fast rate at100° C. if an inhibitor such as SiO₂ was used to prevent crystallinebonds from forming Once drying was complete, the sand was allowed tocool and the coated media was disaggregated. As a final step, the mediawas pH conditioned to a neutral pH by passing DI water at a pH of 8 to 9(raised with NaOH or a similar base) through the media until the pH ofthe effluent was between 7.5 and 8, above the point of zero charge foriron oxides. This also removed any loose iron coating. It is noted thatthe above mentioned scratch coating is necessary because the granularsubstrate was sand which has a relatively smooth surface. However, othergranular substrates such as crushed limestone have a sufficiently roughsurface that a scratch coat is not required.

The second example is provided by a larger-scale field production. Theabove method is scaled up by using a larger gasoline-powered concretemixer and a gas-fired heater. A 3.0 M ferric chloride (FC) solutioncontaining 1000 ppm silica solution was prepared in sufficient volumesuch that the sand could be completely immersed. Thereafter, heat wasapplied via the gas-fired heater to evaporate the liquid and attach theiron to the sand surface. Typically greater efforts must be made toinsure dryness of the FC treated sand as opposed to the FN treated sandsince FC is significantly more hydroscopic than FN. This method provedfeasible to produce the required 9 tons of OCS necessary for a relatedexperiment.

For each batch, approximately 90 pounds of filter sand was placed in theconcrete mixer with an excess of ferric chloride solution. The amount offerric chloride solution put into the mixture was enough to just coverthe filter sand. The mixture was stirred vigorously and heat applied bythe a gas-fired heater. The gas-fired heater was directed into the mouthof the concrete mixer. The slurry was continuously stirred by theconcrete mixture until the sand was completely dry. Typical drying timefor each batch was 3 hours.

Once dry, the sand was poured from the concrete mixer into a backhoebucket and placed in a tandem dump truck for cooling. In preparation forpH neutralization, complete drying of the sand was essential to ensurethe iron coating would not be removed by the sodium hydroxide in the pHneutralization process. If the sand is not completely dry, the ironcoating washes off easily when put into the NaOH solution.

Since the sand was placed in a tandem dump truck for cooling, it decidedto neutralize the entire truckload at once to reduced handling of theOCS. The dump truck full of OCS was parked facing down a slope and asolution (of approximately 10 lbs. of NaOH per 55 gallons of potablewater) was poured into the truck bed on top of the OCS. The idea was tocreate a bathtub effect to neutralize the sand. The truck bed did leakbut the level of the solution was kept above the depth of the sand withcontinual addition of NaOH solution. Leakage of the truck bed provedbeneficial due to the continual addition of new solution to replaceloss. The new solution was more capable of neutralizing the OCS whilethe used solution was removed from the system. The pH was checked with apH probe at several depths in the truck bed to ensure completeneutralization. Approximately 10 tons of OCS was produced, the largestknown quantity of such material. In the above process, the inhibitingagents were formed by the impurities found in the mixer, the gas-firedheater, NaOH and the construction process in the field to such a degreethat it was not necessary to add additional silica as an inhibitingagent.

Another embodiment deals with substrates having a specific gravity ofless than 1.0. There are a large number of likely substrates having anspecific gravity of less than 1.0. One family of such substrates iswood, with pine having by way of example a specific gravity of about0.35. Another family of such substrates is polymeric compounds.Polymeric compounds may include light weight materials such as foampacking pellets (e.g., polystyrene), which would form a granular mediahaving a specific gravity of approximately 0.2. Polymeric compoundscould also include heavier polymers having a specific gravity of up to0.97. Polymeric compounds could also include polymer-type materialswhich have similar weight, flexibility, and long molecular chains. Ofthe polymer family, it has been found that polyethylene (PE) orpolypropylene (PP) have many characteristics making them suitablesubstrates for the present invention. PE and PP have a specific gravityof about 0.9. It is believed PE, PP, and other similar polymericcompounds are particularly useful when in the form of polymeric floatingmedia filter beads. Normally, polymer beads will have a specific gravityranging between approximately 0.50 and 0.95. One simple example of a“filter” or “clarifier” using floating polyethylene beads can be seen inFIG. 1. In the embodiment of FIG. 1, the filter is a cylindricalgeometry upflow filter, but the filter could utilize many geometries andflow directions depending on constraints such as media type, coating,specific gravity and design intentions. Filters using floatingpolyethylene beads are usually upflow filters such as seen in FIG. 1,but can be downflow filters and have a variety of geometric shapes. InFIG. 1, the upflow filter 10 is filled with floating polymeric beads 12.An influent flow 13 flows into filter 10, through beads 12 (where it haspollution constituents adsorbed and filtered), and exits as effluent 14.While not explicitly shown in FIG. 1, the upflow filter 10 could utilizeany number of methods well known in the art for backwashing the beads.Upflow filters have the advantages of being easily backwashed to preventclogging and are less likely to hydraulically “short-circuited” (i.e.water cutting an uninterrupted fluid path through the beads and nothaving to flow around the individual beads). It has been found thatallowing a layer of sediment to form at the base of the filter media mayactually enhance filtration as long as the layer does not become sothick that the layer significantly inhibits design flows. The filtermedia would be backwashed at the point design flows were significantlyinhibited. It is also very practical to direct water through an upflowor downflow filter when the water is being drained from a elevated grade(such as a highway overpass or an elevated interstate). A media bedformed of a granular material such as sand, polymer beads, or othergranular materials will have a given porosity. In one embodiment, thisporosity will be between about 0.1 and about 0.6 while in anotherembodiment the porosity will be between about 0.2 and about 0.5.However, the present invention includes larger porosity ranges and anysub-range between about 0.1 and about 0.6.

The present invention encompasses virtually any filtration system wherea contaminant containing aqueous stream is passed through media havingsome type of amphoteric coating applied thereto. In one embodiment, thecontaminant containing aqueous stream is formed substantially of urbanrunoff. The sources of “urban runoff” as used herein means an aqueousstream from diffuse sources such as rainfall runoff or snow melt andpoint source overflows such as sewer overflows, wherein the stream indirected through an open drainage system (as opposed to a closeddrainage system such as a sanitary sewer). In one embodiment, thecontaminants are phosphorus and/or metal ions, complexes or particulatesand the media is coated with an oxide of aluminum, iron, manganese, orsilicon. The contaminants could be negatively or positively charged ionsor complexes or particles. In another embodiment, the media is coatedthrough a process where a crystal inhibiting compound is added.Preferably, the crystal inhibiting compound raise the SSA of the coatedsubstrate to at least 5 or 10 m²/g and more preferably to at least 20m²/g.

As used herein, “coating” or “coated onto” means a film formed on thesubstrate. The film need not cover the entire substrate, but where itdoes cover the substrate, the coating is “cohesive” and “adhesive”. Thisis distinguished from a series of discrete particles spread on asurface, but not being cohesive. Normally, a coating will cover asignificant part of the substrate. If the substrate has internal surfacearea, the amphoteric substance will form a film on the internal surfacearea of the media substrate. This film also need not cover the entireinternal surface area of the substrate, but where it does cover theinternals surface area, the film is cohesive and adhesive.

One preferred method of applying the amphoteric compound to thepolyethylene is similar to that used to apply iron oxide to sand and isas follows. A 0.5 to 5 molar solution of FN or FC (preferably about1.6M) is prepared by dissolving the FC or FN in water. The polyethylenebeads are placed in the solution and continuously stirred. Thepolyethylene should remain in the solution a sufficient time for theentire surface area of the polyethylene to become coated with ironoxide. An hour should be sufficient period of time under mostcircumstances. The water is then evaporated from the solution containingthe polyethylene at a temperature of approximately 90° C.-95° C. Thedrying may take place at lower temperatures, but will unnecessarily slowthe drying process. Drying at higher temperatures is possible, but maybe undesirable from the standpoint of the polyethylene becomingexcessively plastic at temperatures above 95° C. and crystallization ofthe iron oxide becoming more prevalent at higher temperatures.

One favorable characteristic of employing polyethylene as a substrate isthat polyethylene has an inherent tendency to inhibit thecrystallization of the iron oxide. This is believed to occur by way ofpolyethylene molecules detaching from the substrate surface and becominglodged in the iron oxide molecules depositing on the substrate surface.As alluded to above, this disruption of a uniform iron oxide latticetends to create a favorable, amorphous (thus high specific surface area)coating of iron oxide. In addition to taking advantage of the naturalcrystallization inhibiting character of polyethylene, when using an ironoxide as the amphoteric compound, it may also be desirable to furtheradd an inhibitor such as the 1000 ppm SiO₂ solution discussed above. Theamount of SiO₂ solution may vary, but an amount equal to 1% or less ofthe aqueous volume is normally considered sufficient. If manganese oxideis the amphoteric compound, it usually may not be necessary to add aninhibiting agent to achieve an acceptable SSA. Significantly, it hasbeen found that polymeric beads having a specific gravity of about 0.9maintain a specific gravity of less than 1 (and therefore float) evenafter being coated. The coating generally raises the bead's specificgravity to about 0.95.

While the above procedure described applying an amphoteric compound topolyethylene beads, it will be understood that the procedure could becarried out numerous other polymeric materials. For example, anamphoteric compound could be applied to simple packing material, cheappolymeric woven and non-woven material, geosynthetics, polystryenes andexpanded foams as well. The foams have to be dried at a lowertemperature so they do not melt, so for the case of expanded foams orheat sensitive polymerics, manganese coatings are preferable to ironcoatings (which require higher temperatures to dry).

As mentioned above, another family of amphoteric substances are formedfrom manganese, aluminum or silicon. There are a whole series ofmanganese oxide minerals that can be produced that have usefulcharacteristics as media coatings for the treatment of storm water andother waste streams containing dissolved ionic species, complexedspecies and particulate-bound species such as heavy metals. However, twomanganese oxides groups comprise embodiments for use with the presentinvention because their combination of negative surface charge (measuredas units of charge per surface area) at nearly all environmental pHvalues and because of their high specific surface area. This results ina coated media surface with a high surface density of negatively chargedsites for adsorption of heavy metals. These two manganese oxides arebirnessite (whose structure is not completely understood, but isbelieved to be in part a layered (MnO₆) structure and cryptomelane,(α-MnO₂) which is a tunnel structure. Both are different manganese oxideminerals having different structures. Although not as critical as withiron oxides, some inhibition of crystallization may be helpful toproduce poorly crystalline structures and higher surface area.

The point of zero charge (pzc) of manganese oxides and their surfacecharge density may in some cases provide advantages of manganese oxidecoatings over iron oxide coatings in the adsorption of heavy metals.Iron oxide coatings only have a negative charge on their surface whenthe pH of the solution surrounding the media is greater than the pzc ofthe coating. For pure iron oxides crystalline minerals, this ranges from7 to 8 depending on the mineral form of iron oxide (i.e. goethite,hematite, etc.) and is a comparatively narrow range. Forsilica-inhibited ferrihydrite this pzc can be between pH values of 5.5to 7.5. For manganese oxides the pzc values are much lower. The pzcoccurs at a pH of less than 5. Reported values of the pure mineral formsare in the range of 2 to 3. FIG. 2 illustrates the pzc for the manganeseoxides Birnessite and Cryptomelane and the iron oxide Goethite. Thus,for manganese oxide coated media there is a strong negative charge attypical environmental pH levels of 6 to 8. This also means that pHconditioning such as rinsing with DI water is usually not necessary formanganese oxide coated substrates.

Those skilled in the art will recognize there are numerous methods ofproducing manganese oxides, aluminum oxides or silicon oxides for use inthe present invention. The following two methods disclose examplemethods of the present invention for producing both birnessite andcrypotmelane.

Birnessite Coating Method (BCM).

The disclosed binessite coating method uses a wet oxidation procedure toprecipitate the colloid of birnessite on the media surface. In otherwords, a solution containing manganese was oxidized to create a MnO_(x)form. Two moles of concentrated hydrochloric acid (37.5%) were addeddropwise and continuously to a boiling solution of 0.5-M potassiumpermanganate in 1 liter of water, to which 0.5 liters of media wasadded, immersed and vigorously stirred. The media actually used includedplastic beads, sand, GAC, concrete blocks and concrete rubble. However,any other suitable media (wood, etc.) could also be used. After boilingfor 10 minutes further, the media was washed with water and dried atroom temperature overnight. Under lab conditions, a reasonably pure formof birnessite can be produced (>80% pure). This produced a coatinghaving a surface area of 70-90 m²/g (i.e. surface area of coat asapplied to the substrate) with a pzc at a pH near 3. At environmental pHvalues the surface charge density is very negative (−10 to −20micromoles/m²). This coating has an approximate mean of about 1200micromoles of negative charge per gram of coating.

Cryptomelane Coating Method (CCM).

The Cryptomelane coating method uses a wet oxidation procedure toprecipitate the colloid of cryptomelane on the media surface. A solutionof 0.35 moles KMnO₄ in 800 ml of water is heated to 60° C. and dropwisecontinuously added into a solution 0.5 moles of MnSO₄ in one liter of 2Macetic acid. This solution was heated with 500 ml filtration media (suchas acid washed polyethylene beads or any of the media types named above)to 80° C. while vigorously stirring. After stirring for 15 minutes, themedia was removed, filtered, washed with water and allowed to dry atroom temperature overnight. Under lab conditions a reasonably pure formof cryptomelane can be produced (>80% pure). This will produce a coatinghaving a surface area of 200 to 270 m²/g (i.e. the surface area of thecoating itself rather than applied to the substrate as above) with a pzcat a pH near 3 to 4. At environmental pH values the surface chargedensity is negative (−2 to −5 micromoles/m²). This coating has anapproximate mean of about 823 micromoles of negative charge per gram ofcoating.

It will be understood that one factor is the combination of specificsurface area and surface charge. The difference between 1200 and 823 maybe important when these coatings are applied consistently as with achemical process operation. It should be noted that at the upper end ofenvironmental pH values, ferrihydrite (iron oxide) has a surface area ofbetween 200 and 300 m²/g and a surface charge density of −0.1 to 1.0micromoles/m². Silicate (a form of silica) contamination (addition ofsilica solution or natural silica in clay minerals), tends to preventferrihydrite from transforming to other iron oxides and thus tends tokeep the pzc at a pH of around 5.5 to 7.5, as is typical forferrihydrite. This coating has an approximate mean of about 113micromoles of negative charge per gram of coating. However, the cost ofan iron oxide coating is approximately 1/10 to ⅕ of a manganese coating.This cost does not include the cost of pH conditioning of the influentfor iron oxides which can be significant for engineered systems.

Those skilled in the art will recognize that there is a variety ofsynthetic manganese oxide minerals as there is with iron oxide minerals.However, manganese oxides have not been as well studied as iron oxides.Technically, the term “birnessite” is used to refer to a group ofmanganese oxides for which the exact structures are still to a certainextent unknown. What is known is that these birnessite minerals arelayered structures. Examples of birnessite minerals having a valence >+4are vernadite, ranciete, buserite, and lithiophorite. Examples ofbirnessite minerals with a valence <+4 are magnetite and hausmannite.The other manganese oxides are tunnel structures. One of the more commonis cryptomelane which forms a group of manganese oxides along withhollandite and coronadite (all having ∀-MnO₂ structures with a largeforeign cation (K, Ba or Pb respectively) as part of the structure).Other minerals include ramsdellite (∃-MnO₂), Nsutite (Δ-MnO₂),romanechite (MnO₆) and todorokite. All of these minerals have negativesurface charges and have SSA's that fall in the range of 50 to 280 m²/g.Birnessite and cryptomelane are easy to produce and provide a goodcombination of negative surface charge and SSA for adsorption ofcationic species (mainly heavy metals) when the pH is above the pzc (seeFIG. 2). Naturally, it will be understood that altering the pH to abovethe pzc will facilitate removal of cationic species while altering thepH to below the pzc will allow the removal of anionic species such asnitrite (NO₂ ⁻), nitrate (NO₃ ⁻), or (PO₄ ⁻).

It will be recognized the choice between iron oxide and manganese oxidepresent a typical design choice which will be governed by the particularengineering problem being addressed. Additionally, differentconcentrations of the metal oxides have been used in the solutions inwhich the substrate is immersed. The concentrations may range from 0.1 Mto 3.0 M (or higher) solutions of the metal oxide. Nor is the inventionlimited to immersing the substrate in a metal oxide solution. Rather,the oxide solution could be an aerosol which is spayed onto thesubstrate. This technique works well in a reactor that fluidizes themedia using a gas such as air. The oxide coating is injected as a finespray onto the fluidized media. Once the media is coated, thetemperature in the reactor would be raised to evaporate off the waterand leave the oxide coating on the media. The media will continue to befluidized throughout this process. The reactor can be as simple as anupflow column or a conical upflow reactor. A significant advantage ofthis technique is the savings created by the efficient use of thecoating material.

Still further amphoteric compounds within the scope of the presentinvention are oxides of silicon, particularly as SiO₂ or “silica.”Silica has a point of zero charge (pzc) at a pH ranging between about 2to 4 depending upon the mineralogy and morphology of the silica. Thus,silica carries a strong negative charge at neutral pH. Specific surfaceareas of silica range between 10 and 300 m²/g and can be substantiallygreater depending on the particle size and morphology of the silica,reaching 1000 m²/g or higher. When silica is applied as a surfacecoating, the surface morphology is far less dense than for silica sand,whose surface has been significantly abraded. This is why a silicacoating may have a very high specific surface area while silica sand hasa very low specific surface area. A silica coating may be formed onvarious substrates in manners similar to those mentioned above inregards to oxides of aluminum, iron, and manganese. For example, thesubstrate could be immersed in an about 0.1 M to about 5.0 M solution ofsodium silicate and then the substrate heated to dryness in order toform the silica coating. Naturally, many compounds other than sodiumsilicate could be employed, non-limiting examples being calcium silicateor pure silica. Additionally, higher specific surface areas may beachieved by techniques such as applying the silica solution to the mediaas an aerosol spray at elevated temperatures (e.g. 100° C. or higher).

Although not as common as iron oxides or manganese oxides, aluminumoxides may also be a viable oxide coating, especially on materials suchas CPP. The chemistry of aluminum oxide indicates that it should be aviable material and the cost of this material is relatively low.Therefore, aluminum oxides (such as forms of Al₂O₃) or aluminum saltssuch as aluminum nitrate used to make amphoteric coatings or admixturesare intended to come within the scope of the present invention. Methodsof preparation from aluminum salts are similar to iron discussed above.

The advantage of various alternative embodiments of the presentinvention will become apparent as those skilled in the art begin topractice the invention. For example, using cementitious porous pavement(CPP, discussed below) as the filter media or coating substrate allows aunique manner of avoiding the cost of pH conditioning of the influent.As is well known, cement is largely composed of alkalinity-producingsubstances and therefore is capable of pH elevation. One method is tocoat only the bottom 80% of a CPP pavement block with iron, manganese,silicon or aluminum oxide or combination thereof. Then, as pavementrunoff percolates down through the upper exposed cementitious materialnear the pavement surface, the pH of the percolating runoff will beelevated above the pzc of the oxide coating on the lower half of the CPPblock and thus, the lower 80% of the CPP block form an efficient passivefixed sorption matrix.

Those skilled in the art will recognize many design issues which applyto the choice of substrates or filter media. As discussed above, themedia may be many materials such as sand, polymeric media, clay, pumice,perlite or a fixed porous matrix such as cementitious porous pavement(CPP). Typically, the prior art is only concerned with makingcementitious structures (e.g. pavement) as impervious to water aspossible. However, one aspect of the present invention is creating acementitious material which is quite porous either as a pavementmaterial or as a media substrate. A wide range of size and gradation ofmaterial may be used as media and CPP blocks may be used in their blockform or broken up to serve as a rubble or discrete media substrates.Issues such as contact time, contact surface area, filtration ability,porosity, stress-strain characteristics, pore characteristics,durability and hydraulic conductivity required will determine the choiceof media substrate or rubble size. Any of the above described amphotericcoating preparation techniques may be applied to CPP material either asthe material is being produced (described below) or after the materialhas been produced without a coating (in large or small blocks or assections). If the CPP material is not produced with the amphotericcompound as an admixture (defined below), the block of material will beimmersed in the amphoteric coating solution of choice and the solutionis circulated through and around the CPP block. Because of contact timeissues, one preferred method requires the intact CPP blocks to remain inthe circulating Fe, Mn, Al or Si salt or oxide solution or combinationsthereof for approximately 60 minutes before removing and elevatedtemperature and/or forced convective drying. Drying may also take placeat room temperature for several days under still air conditions or for24 hours when air is being blown by both sides of the block.Alternatively, the porous block could be sprayed with an oxide coating,allowed to dry at ambient or elevated temperature, and then be used. Asused herein, a media having an amphoteric substance “applied” theretoincludes coating (e.g., by spaying, soaking, or immersing) the media;having the amphoteric compound added while producing the media (e.g., asan admixture); or any other method of combining the amphoteric substancewith the media. An “admixture” for the cementitious material (either CPPpavement or CPP as media) for the particular embodiments describedherein may be defined as an amphoteric substance (for example a metalsalt or metal oxide) other than the primary components (e.g., water,aggregate, cement) of cement-based materials such as concrete, where theamphoteric substance is added to the mix design before or during themixing process of the primary components to produce desired modificationto the properties and behavior of the CPP pavement or media. Theadmixture is distinguished from applying a layer, film or coating of anamphoteric substance in that application of such a layer, film orcoating onto CPP pavement or media is carried out after some degree ofhydration (curing) has occurred.

The CPP should be sufficiently porous to allow migration of waterthrough the pore space, but retain sufficient strength to withstandvehicle wheel loads typically encountered by pavement systems that carryvehicular, animal or human traffic; for example road-side shoulders,roadways, parking areas, driveways or sidewalks. One measure of theability of CPP to allow the migration of water is saturated hydraulicconductivity (K_(sat)) measured in cm/sec. In one embodiment, thehydraulic conductivity of the CPP could range between about 1.0 andabout 0.0001 cm/sec or in another embodiment between about 0.1 and 0.001cm/sec or about 0.1 and 0.01 cm/sec. A still further embodiment has ahydraulic conductivity of about 0.01 cm/sec. While there may besituations where a very high hydraulic conductivity is desirable, thismust be balance against concerns with sufficient structural strength andsufficient surface area contact time between the pavement and the fluidflowing through it to insure mass transfer and/or filtration by thepavement. The factors affecting the porosity of the CPP are the water tocement ratio, cement to aggregate ratio, whether and how much pressureis applied during curing, aggregate gradation, aggregate moisturecontent, and to a lesser degree, the amount of fine aggregate in themix.

It will be understood that CCP having a hydraulic conductivity asdescribed above will also have a certain total porosity. Total porosity(or simply “porosity”) may be defined as the ratio of pore volume in amaterial to the total volume of the material. In one embodiment, the CCPdescribed above will have a porosity of between approximately 0.1 and0.6, while another embodiment has a porosity of between approximately0.2 and approximately 0.4. Other embodiments may include any porositysub-range between approximately 0.1 and approximately 0.7.

While there are many mixtures which would form the CPP of the presentinvention, three preferred mixtures are disclosed below in Table 1. Thewater cement ratio for each mix design is varied, ranging from 0.14 to0.32. However, these water cement ratios were used in conjunction withsteam curing as described below. Those skilled in the art will recognizethat if steam curing is not used, the chosen water cement ratio would behigher, up to a water cement ratio of 1. Nevertheless, to maintain ahydraulic conductivity of between 1.0 and 0.0001 cm/sec., it issuggested that the water cement ratio be maintained below 1, although awater-cement ratio of greater than 1 is not excluded from the presentinvention. When CPP is used as a cast-in-place material (i.e. not steamcured and cured at ambient temperature and pressure) a water cementratio of about 0.3 to about 0.4 with wetted aggregate would be onepossible range.

Typically, the ratio of fine to course aggregates will be approximately1 to 1. While this ratio could vary, an excessive amount of fines maytend to reduce porosity by filling passages in the cement structure andreducing the fine aggregate will result in larger pore openings. As anillustrative sample, the grain size distribution of the pea gravel andsand used in Batch 2 is presented in FIG. 3.

TABLE 2 Mix Designs for Porous Pavement Block Component Batch 1 Batch 2Batch 3 Cement   109 kg   109 kg   109 kg (Type II)  (240 lbs)  (240lbs)  (240 lbs) Water 15-20 kg 20-25 kg 30-35 kg Coarse   472 kg   381kg   431 kg Sand (1040 lbs)  (840 lbs)  (950 lbs) # 9 Gravel   336 kg ——  (740 lbs) Pea —   381 kg   331 kg  (840 lbs)  (730 lbs) — Indicatesmaterial not used in batch

The pavement resulting from the disclosed mixes was formed in varioussizes of precast blocks, for example 24 inches×16 inches×4 inches thick.Naturally, this should by no means be considered an optimal size, butrather dimensioning of the blocks will depend on the application. Inthis example the blocks were subject to a conventional pressurized,steam curing process. The process incorporates a press using hydrauliccompression to press the concrete mix into the block form. The hydraulicpress was capable of exerting up to 35 kN (4 tons) of force on the wetcementitious mix in the form and the full 4 tons was applied in thisexperiment. Typically this pressure was applied for 1 to 4 minutes. Thenthe precast CPP blocks were steam cured (in a kiln with over 90%humidity) for four days to a week to promote adequate cement hydrationand then the blocks were allowed to air dry for two days beforetransport. Longer steam curing up to 28 days will produce a higherstrength material. Of course, there is a substantial amount offlexibility in the application of these various components in makingCPP. For example, although the experiment above used 4 tons of force (orabout 3000-lb/ft²) applied for approximately 1-minute, both the forceand duration of the loading can vary based on the application. Thoseskilled in the art will recognize many applications that may requireless force or applications requiring more or less duration of theloading. Precast units and blocks can also be made on-site in molds atambient pressure and temperature however material properties can be morevariable than in a machine-controlled process.

From each porous pavement mix design, a block was sampled at random todetermine the strength and infiltration capacity. From each block fivecores are drilled using a 8 cm (3 in.) outside diameter diamond tippedcoring bit. This yielded cores approximately 7 cm (2.75 in.) indiameter. The infiltration capacity of the porous pavement blocks wasevaluated by the falling head permeability test for soils. Each core waswrapped with an impermeable membrane to determine hydraulic conductivityof the block. Flow was introduced from the bottom of the sample toensure complete saturation. Two trials were taken for each coreresulting in ten hydraulic conductivity values for each porous pavementmix design. As shown in Table 3, Batch 2 has the greatest hydraulicconductivity. Blocks tested later as full blocks had a full blockK_(sat) of approximately 0.01 cm/s.

Since the CPP on the roadway shoulder may be subject to occasionaltraffic loads (or many wheel loads in the case of parking areas), blockstrength is an essential consideration in the design. The unconfinedcompression strength of the blocks was evaluated. Two of the five coresfrom each mix design were tested to determine the unconfined compressionstrength. Since the length to diameter ratio of the cores was less than1.8, the strength was reduced by applying the appropriate correctionfactor as designated in ASTM C-39. The resulting compression strengthsof the three batches are seen in table 3.

TABLE 3 Measured Characteristic of the CPP Blocks Average UnconfinedAverage Hydraulic Compressive Mix Design Unit Weight Conductivity(cm/sec) Strength Batch 1  14.8 kN/m³ 0.0091 37,500 kPa (93.9 pcf) (5440 psi) Batch 2  14.1 kN/m³ 0.0098 27,700 kPa (89.6 pcf)  (4020 psi)Batch 3  14.6 kN/m³ 0.0090 33,600 (93.0 pcf)  (4880 psi)It is noted that these are only a few examples of measuredcharacteristics of CPP blocks. In other blocks, it is envisioned usingCPP where the hydraulic conductivity values are designed either higheror lower than the above values by adjusting the water to cement ratio oradjusting the fine to course aggregate ratio.

Previously described was a process of creating CPP blocks and thencoating the blocks with an amphoteric compound by soaking the blocks ina solution containing the amphoteric compound or spraying on anamphoteric solution. However, the amphoteric compound could also beincorporated in the CPP as part of the process of mixing thecement/aggregate slurry; as an admixture. An example of this methodfollows.

In a shallow container of large surface area compared to depth (in thelab environment, shallow glass trays in the range of 12×16 inches wereused), there is placed a solution of 0.1 to 5.0 molar solution of ametal salt or oxide or combinations of metal salts or oxides. Thesolution can be made by either method described above. To this solution,add a total of 1-kg of cement, and aggregate at the water/cement ratioand cement/aggregate ratio of choice to produce concrete of the strengthand porosity desired. Those skilled in the art will understand thatwhatever volume of amphoteric solution is added should count toward thetotal water cement ratio. For example, using 1 kg of cement and a watercement ratio of 0.5, the adding of 0.25 kg of amphoteric solution willrequire an additional 0.25 kg of water to be added. The mixture is thendried (i.e. the cement is hydrated and the concrete mixture hardens)approximately 12 hours. It should be noted that at least part of thewater in water-cement slurry is actually the solution of metal salt oroxide or combination thereof. In effect, the entire cementitiousmaterial is coated inside and out side with an amphoteric coating. Thesame method could be carried out for an iron oxide or silica coating butwith the one difference; the CPP or cementitious media must be dried atan elevated temperature of 90 to 100° C. for at least 24 hours. As withall media discussed above, if an iron oxide or silica coating is notfully dry before rinsing, some of the coating will be washed off. Whilethis is also a concern for manganese or aluminum oxide coatings it isless of a concern since these oxides usually bond far better tosubstrates such as CPP (and prepared polymer beads) than iron oxides.When the amphoteric compound is included in the concrete mix in asufficient amount as an admixture, the occurrence of the amphotericcompound on the surface of the concrete media is sufficiently dense anduniform over a substantial part of the media surface such that theamphoteric compound acts as and should be considered a “coating” as thatterm is used elsewhere in this application.

With cementitious material as a porous matrix (i.e. as a substrate),final pH conditioning of the iron oxide coating is usually not requiredbecause the alkaline nature of the cement raises the pH to acceptablelevels. In fact, the acidic nature of the iron oxide solution (and to alesser extent the manganese or aluminum solution) actually creates moreinternal porosity of the CPP by consuming a portion of the cement matrixthrough a neutralization reaction. However, this increased internalporosity may also result in a reduction in the cement matrix's strength.This is problem which is less prevalent when manganese, aluminum orsilicon is the base metal salt, or combinations thereof, for theamphoteric substance or compound.

One useful application of a CPP coated with an amphoteric compound is asa paved area, parking area or roadway shoulder filtering section. Forexample, FIG. 4 illustrates a cross-section of a typical roadway. Theroadway will have driving lanes 5 with shoulders 4. In the embodiment ofFIG. 4, the shoulders are formed of a CPP having an amphoteric compoundcoating as described above. Typically, the CPP shoulder will have athickness ranging from 4 to 16 inches. Rainfall-runoff or snowmeltdepicted by arrows 6 will flow off of the driving lanes 5 and onto theCPP shoulders 4. The runoff will infiltrate and percolate into the CPPmaterial and dissolved ionic species, complexed species orparticulate-bound species will be sorbed or filtered by the amphotericcompound on the CPP material. The intercepted runoff that has beentreated will then flow out of the side and bottom of the CPP shoulders4.

Another application of cementitious material or concrete produced withan amphoteric solution is use as a crushed aggregate filter media. Inother words, the object is not to have water flow through the individualpores of a concrete block, but to have it flow around broken up concreterubble. To create a concrete media or cement media that is fullyimpregnated with manganese, the water-cement ratio would be higher toensure sufficient cohesive and adhesive bonding within each piece ofmedia. In this situation, the water cement ratios are close to that ofstandard concrete mixes and a preferred range would be 0.30 to 0.90.This water cement ratio includes the aqueous solution gained from theadmixture. This will be referred to as the “aqueous solution cementratio” to imply that both water and the admixture solution areconsidered in computing the ratio. The concrete would be mixed as aboveand once it hardens (from example, after 12 hours), it is broken up asrubble into media sizes of choice. In certain embodiments, these sizescan range from 0.1 to 10 mm, but sometimes larger, up to 100 mm or moreand other embodiments could include any sub-range between 0.01 and 500mm. If the amphoteric admixture did not provide sufficient amphotericsubstance on the accessible surfaces of the rubble, the rubble couldthen be coated with a layer of amphoteric compound such as describedabove in regards to polyethylene beads. It will be understood that a bedof granular porous pavement will have an enhanced porosity as opposed tolargely impermeable media pieces (e.g., polymer beads). Granular porouspavement media will have pores between discrete pieces of media inaddition to the pores within the pieces of media themselves. In oneembodiment, this combined porosity of the media is about 0.1 to about0.6 for media with little internal porosity and in another embodiment isabout 0.2 to about 0.8 for media with internal porosity.

In other embodiments, polymeric compounds or organic-based materialsthat include light weight materials with a specific gravity of less thanabout 1.0 and in other embodiments, less than about 0.9 can be appliedwith a thin cement paste that contains an amphoteric substance (e.g.,manganese, iron, aluminum or silica based). There are at least twomethods by which the amphoteric substance may be applied. First is a twostage process: 1) a thin cement paste which hydrates and hardens(preferably in hours) is applied to the media; and 2) then the media iscoated with a solution containing an amphoteric substance of manganese,iron, aluminum or silica. In a single step process, the cement mixcontains an amphoteric compound solution as an admixture (prior to thecements application to the substrate) in order to produce the amphotericsubstance on or in the substrate. In either case, the resultingpolymeric or organic substrate and coating has a net specific gravityless than 1.0 and floats under quiescent conditions. Both the cementcoating and solution can be applied in serial processes with hydrationused as an intermediate step between the two applications.

Another method of coating the CPP (or other substrates) includesrecoating the media. One example of recoating the media was accomplishedby placing the media in a column in which it will be fluidized with arecirculating flow of manganese solution. Thus, 1-kg of media was placedin a vertical column (the column was approximately 2 liters in volume)with a 6-liter recirculating solution of 10⁻³ M NaHCO₃ and0.035-moles/liter Mn²⁺ (stoichiometric amount) and re-circulating thissolution with a pump capable of handling aggressive solutions and with asufficient capacity to fluidize the bed. The Mn²⁺ is oxidized by adding250-mL of a 0.185 M solution of NaOCl at a flow rate of 5 mL/minute for1 hour to ensure complete oxidation of the manganese. The manganeseoxide in this solution is then re-circulated for an additional 2 hourswith 250-mL of 0.185 M NaOCl added in one step at the beginning of the 2hours. After 2 hours, the solution was drained and then replaced withwater (in the lab, it was de-ionized (DI) water) and re-circulated for15 minutes and then the column was drained of the water solution. Themedia was then rinsed with water (DI in lab) to a pH of 7 and thenallowed to dry overnight before use. The rising of a manganese oxidecoated media with DI water was mainly to remove impurities in order toobtain laboratory quality samples. In practical field applications, thefinal rinsing of manganese oxide coated media could be dispensed with.

Naturally, re-coating of the media is not limited to manganese oxideupon manganese oxide. Another re-coating method would include a firstcoating with iron oxide followed by a second coating of manganese oxide.If the iron oxide coated material produces a sufficiently high SSAsubstrate for the intended application, this latter method may be moredesirable since iron oxide is normally less costly than manganese oxide.Thus, a comparatively inexpensive substrate such as sand with a low SSAmay be coated with iron oxide to produce a comparatively high SSAsubstrate (i.e. a substrate with a SSA much greater than 0.1 m²/g). Inother words, the iron oxide coated sand becomes the substrate for thefinal filter media which is coated with manganese oxide. Additionally,the increased SSA achieved by re-coating may be applied to any of theabove disclosed substrates (CCP, wood, polymers, etc.) or with otheroxides of metals such as aluminum, silica or other surface activematerials of high surface area and amphoteric nature. A combination ofcoatings can allow the same media or CPP system to incorporate sites foradsorption of cations and anions.

The scope of the present invention also includes coating formed ofcombinations of silica with different amphoteric compounds. For example,a substrate could be immersed in a solution containing silica (e.g.about 0.1M to about 5.0M) and aluminum oxide (or iron oxide or manganeseoxide, again at example molarities of about 0.1M to about 5.0M) and thenheated to dryness. The ratio of silica to aluminum (or iron ormanganese) oxide in the solution could vary depending on the ultimateuse of the coated substrate, but in one embodiment the ratio could be 1to 1. However, the solution ratio could vary depending on the desiredratio of total positive charge versus total negative charge at a giventarget pH. Alternatively, the aforementioned solution could be anadmixture to a cementitous porous pavement (CPP) formulation asmentioned earlier in this specification.

A combination coating could also be formed by a serial process. In otherwords, first submersing the substrate in a silica solution (and heatingto dryness) and then submersing the silica coated substrate in analuminum (or iron or manganese) oxide solution before heating todryness. It will be understood that coatings are not normally completelycontinuous over the entire surface of the substrate. Imperfections willresult in breaks in the upper coating (aluminum oxide coating in theabove example) allowing the lower coating to be exposed to theenvironment and bond with ions or complexes of the appropriate charge.Naturally, the serial embodiment of the invention is not limited to asilica coating followed by another coating, but could be formed in thereverse order. Nor are the combinations limited to including silica, butcould be combinations of iron, aluminum, or manganese oxides with nosilica present. Likewise, anywhere in this description where oxides ofiron, aluminum, manganese, or silicon are described, it will beunderstood the invention could alternatively include non-oxide states ofthese metals and could include any method of applying one or more ofthese metals to a media substrate.

Rather than coating the same substrate particles with a combination ofamphoteric compounds, a similar effect may be obtained by mixingsubstrate particles having different compounds coated thereon. Forexample, a first quantity of media could be coated with aluminum oxideand a second quantity of media coated with silica. To form the finalamphoteric compound coated filter media, the two types of sand would bethoroughly mixed. An alternative embodiment could comprise differenttypes of filter media in alternating layers. For example, FIG. 5Arepresents a filter column 15 having alternating layers 10 of aluminumoxide coated sand and layers 20 of silica coated sand and a contaminatedwater stream 9 flowing therethrough. Naturally, the same type filtercould be implemented using other coated media such as crushed CPP orpolymer beads as disclosed above. Rather than a filter column with adiscrete particle filter media, the same concept could be carried out ina CPP block having a contaminated water stream 9 flowing therethrough.The CPP block 30 is formed by first submersing the lower half 30 a ofblock 30 in an aluminum salt or oxide solution (and allowing to dry) toform coated layer 32. Then the upper half 30 b is submersed in a silicasolution to form coated layer 34. When a contaminated waste stream 9passes through the porous pavement material, the stream first encountersthe aluminum oxide coated layer and then encounters the silica coatedlayer.

Naturally, there are many different ways to achieve the effect of twodifferent coatings. For example, the block 30 in FIG. 5B could be formedusing an admixture of silica solution in the cement mix, thus causingthe entire block to initial have a silica coating. Then, the lower half30 a could be immersed in an aluminum oxide or salt solution, causinglower half 30 a to have an aluminum oxide coating. These and all othermethods of obtaining a combined coating of two different amphotericcoatings are included in the scope of the present invention. It willalso be understood that by using amphoteric compounds with differentpzc's at a given pH, it will be possible to have substrate layers havingdifferent net charges. For example, at a neutral pH, silica will have anet negative charge for removing positively charged metal contaminantswhile aluminum oxide will have a net positive charge for capturingnegatively charge contaminants.

Other embodiments of the present invention include not only coating aCCP block through its entire depth, but also coating only a fraction ofthe overall depth of the block. For example, the upper area 30 b in FIG.5 could be coated with one of the above mentioned amphoteric compounds,when the lower area 30 a is left uncoated. The coated depth could be aslittle as half an inch, but more typically will be one half or more ofthe total depth of the CCP block.

Additionally, substates could be formed from any porous structure havinga fixed matrix. An example of such a porous fixed matrix would besolidified lava (lava rock or pumice). A fixed matrix having a porosityof between 0.05 and 0.6 would be one embodiment of the presentinvention.

The present invention may be put to enumerable uses. For example, whilethe above disclosure discusses a cementitious porous pavement material,the porous pavement material could also be bituminous or asphaltic.Porous asphalt can be made by reducing the asphaltic binder and, ineffect, producing a lower binder-aggregate ratio. Typically, theamphoteric compounds described above may also be added to the bituminousporous pavements during the mixing stage, creating the same type ofwaterborne metals filter. However, with all porous materials, anamphoteric material can always be added as a surface coating and much ofthe porous surface can be coated by application of a spray on the poroussurface. If practical to immerse the asphalt material in an amphotericsolution, the amphoteric solution may be applied in this manner. As usedherein, “immersed” does not necessarily mean the entire volume beingcompletely submerged in a solution, but also includes dipping only apart of the media volume in a solution.

Large areas of porous pavements may also be used as storm water storagebasins. Parking lots and similar large paved areas are often the sourceof significant volumes of rainfall-runoff or snowmelt. The porouspavement of the present invention provides a means of substantiallyreducing the volume of runoff or snowment from such large pavementareas. These areas may be defined as a ratio of their length to width.In certain embodiments of the present invention, a storage basin may beany pavement area having a length to width ratio (i.e. length/width) ofless than 20. A typical parking area formed of porous pavement couldhave a porous pavement with a hydraulic conductivity of between 0.0001cm/sec and 1.0 cm/sec and more preferably of around at least 0.001cm/sec. Because it is not necessary to transfer the water so quickly inparking areas, it may be preferred to have higher strength and lowerhydraulic conductivity. Porous pavement having a hydraulic conductivityof 0.0001 cm/sec. and 1.0 cm/sec will normally have a 28-day unconfinedcompressive strength in one embodiment of between approximately 2000 and6000 psi and in another embodiment between approximately 3000 psi and5000 psi. The porosity of the pavement in one embodiment will be betweenapproximately 0.1 and 0.6 and in another embodiment betweenapproximately 0.15 and 0.5, and in a third embodiment betweenapproximately 0.2 and 0.35. In one embodiment, such a layer of porouspavement could be at least four to eight inches in depth and in anotherembodiment, at least twelve to fifteen inches in depth. This depthprovides both the necessary strength to support vehicular traffic andalso provides a sufficient volume of pore space to store the water froma water quality rainfall-runoff event With a porosity of 0.15 to 0.35, a6 inch slab of porous pavement could retain as much as 1 to 2 inches ofrainfall in that slab. Rather than placing further strain on stormsewers, the rain collected in the porous pavement will be left toevaporate during dryer days. This method of storing runoff from parkinglots has the further benefit of tending to immobilize parking lotpollutants entrained by the rain water. Rather than leaving the premisesof the parking lot, such pollutants will be retained in the porouspavement. As the water evaporates from the porous pavement over time,the pollutants will tend to be retained in the pavement. Many volatilepollutants may be volatized into the air during evaporation through theCPP material, a process which is preferable to the pollutants becomingdissolved as mobile solutes in water. Additionally, the porous pavementmay be treated with an amphoteric compound in order to improve thecapture of waterborne ionic constituents which are held in the porouspavement while the retained water evaporates. It can readily be seen howa parking lot constructed of porous pavement will form a storm waterstorage basin capable of supporting vehicular traffic.

Another embodiment of the present invention includes a roadway gravelshoulder capable of capturing waterborne ionic constituents entrained inroadway rain runoff. Roadways often have gravel shoulders at least fourinches in depth, more typically six to eight inches in depth and forlarger roadways, often over eight inches in depth. Commonly, the gravelfor roadways is graded to have an average diameter of betweenthree-fourths of an inch to one inch. To carry out one embodiment of theinvention, the gravel may be coated with an amphoteric compound such asone of the iron, manganese, aluminum, or silica oxides disclosed above.In one embodiment, this would be done prior to placing the gravel as aroadway shoulder. Any of the coating processes discuss above would besuitable, but the previously described field method for producing largequantities of iron oxide coated sand would be one preferred method. Thegravel could also be subject to the multiple layer coating alsodescribed above. Once the coating process for the gravel was complete,the gravel would be placed along the roadside in the normal manner forcreating a shoulder. This manner of capturing waterborne ionicconstituents is advantageous because it can passively filter and treatpavement sheet flow directly at the edge of the pavement before the flowbecomes concentrated.

A still further embodiment of the present invention encompasses coatinga flexible, planar, porous substrate with an amphoteric compound. Oneexample of a flexible planar, porous substrate would be geosyntheticfabrics which are well known in the art. Geosynthetic fabrics aregenerally polymeric materials which are designed to be placed in oragainst soil. Often geosynthetic fabrics are used to retain soil inplace while allowing water to pass through the fabric. Geosyntheticfabrics may be woven or nonwoven. Woven geosynthetic fabrics are fabricswith filaments in warp (machine direction) and weft (cross-machine)direction. Nonwoven fabrics have essentially a random fabric or textilestructure. For example, common felt is a nonwoven textile. Nonwovens arefurther characterized according to how fibers are interlocked or bonded,which is achieved by mechanical, chemical, thermal or solvent means.Some of the polymeric materials used to construct geosynthetic fabricsinclude: polyethylenes—PE, HDPE, LDPE, XLPE, FLPE, CPE, CSPE;polypropylene—PP, polysulfone—PSF; polyurethane—PUR; polycarbonate—PC;polyvinyl chloride—PVC, polystyrene—PS; thermoplastic elastomer—TPE;nylon—PA; polyester—PET; nytrile; butyl; acetal—ACL; and polyamide—PA.Most typically, geosynthetics are formed from PE, PP, PVC, PET, PA orPS. The application of an amphoteric substance to the geosyntheticscould be carried out by a process similar to that described above forcoating polyethylene beads. However, rather than stirring the beads, thesheets of fabric are dipped in solution, pulled them out of theamphoteric solution, and then dried them. The sheet could be left in thesolution while dried, but this method wastes a substantial amount ofamphoteric solution. With fabric or sheet material, the one techniquewould be to spray on the solution and dry or to dip in the solution anddry.

Geosynthetic materials coated with amphoteric substances can serve asmore effective filters (higher surface area and surface roughness) whichcan adsorb cations (e.g. heavy metals) or anions (e.g. phosphates)depending on the pH of the aqueous stream, seepage, ground water, or thelike. The filters of the present invention can be in-situ or ex-situ. Anexample of an in-situ filter would be where one has shallow contaminatedgroundwater or one is directing a flow of storm water into a trench. Onecan place a sheet of amphoteric substance coated (with or without acementitious coating for the substance) geosynthetic fabric in a trench,backfill around it and let the flow passively move through the trenchand therefore move through the more permeable geosynthetic to providein-situ treatment. Alternatively, a cementitious coating could beapplied to the geosynthetic fabric with the amphoteric substance eitherbeing applied to the cement after drying or as an admixture to thecement during its mixing. Ex-situ filters would be all of those caseswhere one does treatment in some form of a device or reactor, like theupflow column seen in FIG. 1.

Another example of a flexible planar, porous substrate would be membranematerials. Membrane materials typically have much smaller pore sizesthan other filters, commercially available on the order of 0.1 to 50microns and can be up to 3000 or more microns. Often membrane materialsare formed from a type of cellulose such as cellulose acetate, celluloseesters, cellulose nitrate, or nitrocellulose. The amphoteric coating maybe applied as described above for oxide coated geosynthetics. Themembrane substrates may be considered “membrane filters” in the sensethat they capture constituents only on their surface. This isdistinguished from the other substrates described herein which act as“depth filters.” Depth filters capture constituents through some depth(even if relatively shallow) in the substrate.

The flexible planar, porous substrate could also include any number ofconvention filter materials or devices which have a larger areadimension than depth dimension. For example, conventional airconditioning or furnace cartridge filters could be formed by having anamphoteric compound applied to the filter media within the cartridge.The filter media will typically be a fiberous polymeric or glassmaterial woven or meshed together at different densities depending onthe intended use of the filter.

A further embodiment of the present invention includes a drainage pipecapable of capturing waterborne ionic constituents. Most storm waterrunoff is carried through conventional concrete pipes for at least partof the journey to its final collection point. Thus there is theopportunity to bring the runoff into contact with a pipe surface coatedwith an amphoteric compound and remove ionic constituents from thewater. Typically, drainage lines are sized to accommodate a standardrunoff rate which is less than the total capacity of the drainage pipes.In other words, drainage lines are not designed to have the averagerunoff completely fill the volume of the drainage pipe. This means thatless than the entire inner circumference of the pipe is designed to comeinto contact with the runoff water. Therefore, it may not be necessaryto coat the entire interior of the pipe with the amphoteric compound,but rather only coat the portion of the inner pipe surface designed tobe in contact with the water. It will be obvious that the decisionconcerning how much of the inner surface of the pipe should be coated isa engineering design choice which will vary according to the designparameters. One manner of applying the amphoteric compound will simplybe to immerse the section of pipe to be coated in an amphoteric compoundcontaining solution such as disclosed above. For example, the solutioncould be a 1 to 3 molar ferric nitrate or ferric chloride solution or a0.1 to 5 molar solution of either birnessite or cryptomelane, oraluminum or silicon. Alternatively, the amphoteric solution could beapplied directly to the pipe surface by spraying and the like.

The piping could be formed out of conventional concrete or a CPPmaterial such as described above. The CPP piping would most likely beused when the pipe grade was above the water table or placed in soilwhich could otherwise readily absorb runoff. In this manner, runoffflowing through the water could be at least partially returned to theground around the run of the pipeline. The CPP piping could in oneembodiment have a hydraulic conductivity ranging from about 0.0001 toabout 1.0 cm/sec. Both the CPP piping and conventional concrete pipingcould have the amphoteric compound introduced in the mixing processprior to the concrete mixture being placed in the pipe forms. It is alsoin the scope of the present invention to include conventional fired claypiping which has been coated with an amphoteric compound or a speciallymade clay piping which has had the amphoteric compound added as part ofthe clay mixture before the pipe is fired.

Another embodiment of the present invention comprises forming a filterby placing an amphoteric compound in a clay liner or in a roadwaysub-base. As used herein, the term “sub-base” is intended to include aroadway sub-base formed of clay, silt or sand or a mixture of thesematerials or recycled materials. This sub-base may be water pervious orimpervious. Conventionally, a sub-base is formed by placing a layer ofuncompacted soil or recycled material over the area where the sub-baseis to be constructed. Water is then added to bring the sub-base to itsoptimum compacted moisture content. The layer is then compacted to apredetermined density. Typically, this process is carried out in layersor “lifts” as is well known in the art. The optimum compacted moisturecontent is determined by standard testing procedures such as set out inASTM D698. An improved sub-base according to the present invention maybe constructed by raising the uncompacted sub-base to its optimumcompacted moisture content with a solution containing an amphotericcompound. It may not be necessary to add the amphoteric solution to alllifts, but simply the upper most 1 to 3 lifts. Clays have a wide rangeof SSA values ranging from approximately 15 m²/g for clays likekaolinite or illite up to approximately 850 m²/g for clays like sodiummontmorrillinite. Their large SSA values make clays a highly effectivesubstrate for applying amphoteric compounds.

Another geotechnical structure utilizing amphoteric substance could bewater impervious clay liners. While clay liners are intended to be waterimpermeable, it is common for liners to have some permeability resultingin water escaping from within the liner into the surrounding soil. Ifthe clay liner is treated with an amphoteric substance, water travelingalong the liner (toward the break) or through the liner will have ionicconstituents sorbed from it. In a similar manner, some roadways arebuilt with sub-bases which are intended to be water impervious.Generally, it is also not intended to have water flow through thepavement to the sub-base. However, cracking in roadways is commonplaceand rainwater migrates through the cracks to the sub-base. If thesub-base retains its water impermeable characteristics, water will flowlaterally to the edge of the roadway. If the sub-base is coated with anamphoteric substance, ionic constituents are effectively removed as thewater travels along the sub-base toward the edge of the roadway. If thesub-base also forms cracks, water flowing through the sub-base will betreated.

FIG. 5C is a further filter system embodiment of the present invention.Filter system 45 generally comprises rigid filter housing 51 having aninlet 52 and an outlet 53. Positioned within housing 51 is a filtermedia containment 56. In one preferred embodiment, filter mediacontainment 56 is form of a porous flexible material such as ageosynthetic fabric 57 with sufficient strength characteristics tocontain the selected media without tearing or failing. This embodimentof media containment 56 is sized to be generally the same shape as andto fit closely against the walls of housing 51. A handle 58 may beattached to media containment 56 to allow easy insertion into andremoval from housing 51.

In the embodiment shown, media containment 56 encloses a quantity ofgranular media 59. In a preferred embodiment, granular media 59 is acrushed concrete aggregate having an amphoteric compound formed thereon(as described above). A typical size range for the aggregate will beabout 1-10 mm, but is not limited to this size range. The crushedconcrete aggregate could be formed from porous or nonporous cementitiousconcrete. Likewise, granular media 59 could be formed of othersubstances such as sand coated with an amphoteric compound. Naturallygeosynthetic fabric with less porosity would be used when the media issand as opposed to the larger crushed concrete media pieces. In analternative embodiment, floating granular media could also be employed.It will be understood that although FIG. 5C (and FIGS. 6A-8B) areshowing open space within media containment 56, the figures are intendedto convey conceptually that media containment 56 is substantially fullof granular media 59. In each of these configurations lightweight mediawith a specific gravity of less than 1.0 can be applied.

A somewhat different configuration of filter system 50 is shown in FIGS.6A and 6B.

FIG. 6A is a side view of filter system 50 illustrating a rigid filterhousing 51 having an inlet 52 and outlet 53. The filter system of FIG.6A differs from that of FIG. 5C in that there is an interior hollowcolumn 54 which forms an annular space 55 (best seen in FIG. 6B) betweenthe outer wall of housing 51 and hollow column 54. The liquid stream tobe treated enters the top of hollow column 54 and flows downward to exitthrough side openings 60 in the bottom of hollow column 54 and enterinto annular space 55.

Positioned within annular space 55 is the toroidal or ring shaped mediacontainment 56. As in the previous embodiment, media containment 56could be formed of geosynthetic fabric 57 of sufficient strengthcharacteristics, but could also be of any material (flexible or rigid)which contains granular media 59. While in the embodiment shown, mediacontainment 56 is formed of a uniformly porous fabric, other embodimentsof media containment 56 could include other configurations wherein lessthan the entirety of media containment 56 is porous. For example, thetop and bottom of media containment 56 (where fluid must pass) beingporous while the sides of media containment 56 are substantiallynon-porous. As with the previous embodiment, granular media 59 couldcomprise a crushed concrete aggregate having an amphoteric compoundformed thereon, coated sand, or any other coated granular media such asmedia with a specific gravity less than 1.0.

A still further embodiment is seen in FIGS. 7A and 7B. FIG. 7Aillustrates a down spout filter 65. Filter 65 generally comprises aflexible media containment 66 of sufficient strength characteristicsfilled with granular media 68 and having a connecting sleeve portion 69which slides over the terminal end of conventional drainage down spout70. Media containment 66 will generally not be sufficiently porous toallow the passage of water. However, outlet apertures 67 (or a porousarea) will be formed in some portion of media containment 66 (the topportion in the example of FIG. 7A) in order to allow water flowing intomedia containment 67 to exit there from after passing through filtermedia 68.

FIG. 7B illustrates a filter system connected to a bridge down spout 71.The embodiment of FIG. 7B is largely similar to that of FIG. 7A.However, it will be understood that media containment 66 might typicallyhang freely from bridge down spout 71 and must have sufficient materialstrength to support the weight of filter media 68 by way of sleeveportion 69 being firmly clamped to down spout 71. As with the previousembodiment, granular media 68 could comprise a crushed concreteaggregate having an amphoteric compound formed thereon, coated sand, orany other coated granular media. A media formed of amphoteric compoundcoated polymer beads or other lightweight media would be particularlysuitable for the embodiment of FIG. 7B since this would provide theleast weight stress on the hanging media containment 66.

The size and shapes of media containments 66 (and other mediacontainments disclosed in this application) will largely depend on theflow path in which it is desired to direct the liquid. The flow pathshould be sufficiently long to ensure the liquid has sufficientresidence time when passing through the filter media in order to bring asufficient percentage of the liquid borne contaminants into contact withthe filter media. Factors such as the pressure, head loss and flow rateof the liquid, the media size, hydrodynamics, desired residence time,and ultimately performance will affect the size and shape of the mediacontainment.

FIG. 8A illustrates a still further embodiment of the filtration systemof the present invention. In FIG. 8A, filter system 75 consists of agranular media 78 positioned within filter containment 76. In thisembodiment, filter containment 76 will comprise a mesh material 77 whichcould be a porous geosynthetic material, natural porous material butcould also be a wire mesh such as conventional “hardware cloth”,“chicken wire” or chain-link fencing wire. In the typical situationwhere the wire mesh has openings larger than the media particles, afiner mesh such wire window screening could be placed as a liner withinthe larger gauge wire mesh.

In a preferred embodiment, filter containment 76 will be shaped suchthat when filled with filter media, filter containment forms a blockshape. Then filter containment 76 (or several filter containments 76)will be arranged in the flow path of the liquid stream to be filtered.FIG. 8A suggests that the liquid steam is flowing toward the top portionof filter system 75. It can be seen that the filter media 78 in FIG. 8Ais formed of a size gradation of media particles. Toward the center ofmedia containment 76 are coarser media particles (e.g. on the order of25 to 100 mm in diameter) while around the outer sides of mediacontainment 76 are finer media particles 80 (e.g. on the order of 1 to20 mm in diameter). The purpose of these media size differences is toallow freer flow of liquid to the center area of media containment 76and retard the flow of liquid toward the edges of media containment 76.This media configuration will help ensure sufficient residence time ofthe liquid flowing from top to bottom through the media as opposed toliquid taking a shorter side path toward the outer edges of mediacontainment 76.

FIG. 8B illustrates yet another embodiment of the filter system of thepresent invention. Filter system 90 will comprise concrete blocks 91with bore holes 93 formed therethrough. FIG. 8B is a cross-sectionalview and it will be understood that continuous concrete extends aroundthe parameter of blocks 91 to maintain the block's structural integrity.The bore holes 93 will be filled with granular amphoteric compoundcoated media 94 and a porous fabric or wire mesh 95 will extend acrossthe tops and bottoms of bore holes 93 in order to retain the granularmedia therein. As with the previous embodiment, blocks 91 will beposition in the liquid steam path such that the liquid is directedthrough the media filled bore holes 93.

FIG. 8C illustrates a filter system 100 which will generally be employedadjacent to a paved area 101 such as a parking lot or roadway (in whichcase the paved area 101 may act as a roadway shoulder). A trench 105 isformed adjacent to the paved area 101. Trench 105 will have a perforateddrain pipe 105 positioned at its bottom and will be filled with agranular media 103 such as amphoteric compound coated sand. A cap 102 ofcementitious porous pavement will then be placed over granular media103. In operation, contaminant containing runoff from paved area 101will flow across and into porous pavement 102 and then through coatedmedia 103 wherein positively and/or negatively charged (depending on themedia coating) ions and complexes are removed before the treated waterexits through discharge drain 104. As one illustrative example, trench105 could be approximately 60 cm deep, 30 cm wide, and cap 10 cm thick.However, the filter system 100 could take on any dimensions required bythe particular design being implemented.

In certain media embodiments described above where the amphotericsubstance is applied as a coating, the coating may be comprisedpredominately of aluminum, iron, manganese, silicon or combinations ofthese metals (or their oxides) such that the total dry mass of theapplied coating (to external and internal surface areas) is greater than0.05 milligrams per dry gram of media substrate. Multiple layers ofapplied coatings would have a linearly proportional composition per drygram of media substrate. For example, two applied layers would result ina media with a dry mass of applied coating that is greater than 0.10milligrams per dry gram of media substrate.

In certain embodiments where the amphoteric substance is applied as anadmixture, the admixture may be comprised of predominately of aluminum,iron, manganese, silicon or combinations of these metals (or theiroxides) such that the total dry mass of remaining admixture that is acomponent of the media is greater than 0.05 milligrams per dry gram ofmedia.

In one embodiment where the media is coated with a cementitious layer,the cementitious coating shall be such that the total dry mass of theapplied cementitious coating (to internal and external surface areas ofthe media) is greater than 0.10 milligrams per dry gram of mediasubstrate. Multiple layers of applied coatings could have a linearlyproportional composition per dry gram of media substrate. For example,two applied cementitious layers would result in a media with a dry massof applied coating that is greater than 0.20 milligrams per dry gram ofmedia substrate.

In many of the embodiments described above, the total dry mass of theapplied amphoteric substance per dry gram of media may be at least 0.5mg/g and alternatively ranging from about 0.5 mg/g to about 50 mg/g. Inalternative embodiments, amphoteric substance could range from about 1to about 20 mg/g or from about 5 mg/g to about 10 mg/g. Otherembodiments include all sub-ranges between about 0.5 mg/g and about 50mg/g.

Alternative Embodiments

While the foregoing invention has often been described in terms ofspecific examples, those skilled in the art will recognize manyvariations which are intended to fall within the scope of the claims.For example, while the above has described the media as utilized forremoval of dissolved cations and anions, complexed species andparticulate-bound species from water, the media could be utilized toremove many types of airborne or waterborne non-ionic constituents. Inparticular, sand or polyethylene beads filters could readily be adaptedto treat flows of air for ionic constituents such as aerosols, chargedparticulate matter, odors, and gas emissions containing water vapor withanionic or cationic species.

One embodiment of a filtration system for removing negatively orpositively charged ions, complexes or particulates from an aqueousstream, may include: a) an aqueous stream formed substantially of urbanrunoff; b) a filter containment communicating with the aqueous streamsuch that at least part of the stream passes through the filtercontainment; and c) a filter media disposed within the filtercontainment, the filter media comprising an amphoteric material appliedthereto, wherein is amphoteric material is an oxide of at least one ofAl, Mn, Fe or Si. The above filtration system wherein the aqueous streamis a variable stream generated by a rainfall-runoff or snowmelt event.

The above filtration system wherein the aqueous stream has a pH ofbetween about 6 and about 9. The above filtration system wherein thefilter media is a granular media having a total porosity of betweenabout 0.1 and about 0.6. The above filtration system wherein the filtermedia is a fixed matrix media having a total porosity of between about0.1 and about 0.4. The above filtration system wherein the fixed matrixis a cementitious porous material.

The above filtration system wherein the amphoteric media comprises bothan oxide of Si and an oxide of one of Al, Mn, or Fe. The abovefiltration system wherein the Si oxide media and the media comprising anoxide of one of Al, Mn, or Fe are intermixed. The above filtrationsystem wherein the Si oxide media and the media comprising an oxide ofone of Al, Mn, or Fe are positioned in distinct layers. The abovefiltration system wherein the filter containment is formed by a poroustextile (or geotextile) material. The above filtration system whereinthe filter containment is formed by a porous mesh material. The abovefiltration system wherein the porous mesh material is a wire mesh. Theabove filtration system wherein a substantial portion of the aqueousstream is runoff from an urban, constructed, disturbed or paved surface.

The above filtration system wherein the cementitious media has a depthdivided into a first and second portion and one amphoteric material isapplied to the first portion. The above filtration system wherein asecond amphoteric material is applied to the second portion. The abovefiltration system wherein the amphoteric material is applied as anadmixture. The above filtration system wherein the filter systemincludes a rigid media housing and the filter containment is a flexiblematerial generally shaped to fit within the media housing. The abovefiltration system wherein the filter media is a granular media having ahydraulic conductivity of between about 1 and about 0.0001 cm/sec. Theabove filtration system wherein, the filter media is a fixed matrixmedia having a hydraulic conductivity of between about 1 and about0.0001 cm/sec. The above filter system wherein the filter containment isin a toroidal shape.

The above filter system wherein the filter containment is formed bypositioning granular media within a trench and placing a layer of porouscementitious pavement over the media. The above filter system whereinthe filter containment is formed of a mesh material with smallergranular media positioned in the outer portions of the filtercontainment and larger granular media positioned in the inner portionsof the filter containment. The above filter system wherein the filtercontainment comprises bore holes through a rigid matrix material.

An alternate filtration system for removing ions, complexes orparticulates from an aqueous stream would include: a) an aqueous streamcontaining ions, complexes or particulates; b) a filter containmentcommunicating with the aqueous stream such that at least part of thestream passes through the filter containment; and c) a filter mediadisposed within the filter containment, the filter media comprising anamphoteric material applied thereto, wherein the amphoteric material isan oxide of Fe and has a crystal inhibiting agent creating a SSA on thefilter media of at least about 10 m²/gm.

Additional Numbered Embodiments

Numerous additional embodiments are described in the following numberedformat.

1. Discrete Media, Amphoteric Coating of Single Oxide with CrystalInhibitor

One embodiment of the present invention is a sorptive-filtration mediafor the capture of waterborne or airborne constituents and particles.The media comprises a granular substrate and a single amphotericcompound, preferentially an oxide of aluminum, manganese, iron orsilicon bonded to a substrate in the presence of a crystal inhibitingagent.

2. Discrete Media, Amphoteric Coating of Single Oxide without CrystalInhibitor

Another embodiment of the sorptive-filtration media for the capture ofwaterborne or airborne constituents and particles is a media comprisedof a granular substrate and a single amphoteric compound, preferentiallyan oxide of aluminum, manganese, iron or silicon bonded to granularsubstrates in either the absence or presence of a crystal inhibitingagent.

3. Discrete Media, Amphoteric Coating of Mixed Oxides with CrystalInhibitor

Another embodiment of the sorptive-filtration media for the capture ofwaterborne or airborne constituents and particles is a media comprisedof a granular substrate and a mixture of amphoteric compounds,preferentially from oxides of aluminum, manganese, iron or siliconbonded to granular substrates in the absence or presence of a crystalinhibiting agent. The solution mixtures are generally binary mixtures(excluding silicon or other crystal inhibiting agent) of iron andmanganese, aluminum and manganese, iron and aluminum, iron andmanganese, or silicon in combination with either iron, manganese oraluminum. The proportions of the selected oxides will be dependent, inpart, on the surface charge, net point of zero charge (pzc), and therelative population of charged sites (both positive and negative)created by the resulting mineral coating at a given pH, in order totarget a specific constituent or competitive combination ofconstituents. Solution mixtures do not have to be only binary. Forexample, manganese can be added to a binary mixture of iron and aluminumto create a lower net pzc and create a relatively higher proportion ofnegatively charged sites allowing the treatment of both positively andnegatively charged constituents. Certain combinations of oxides willobviate the need for a crystal inhibiting agent. For example, combininga manganese oxide in percentages as low as 1% with an iron oxide caninhibit iron oxide crystal formation.

4. Discrete Media, Amphoteric Coating of Mixed Oxides without CrystalInhibitor

Another embodiment of the sorptive-filtration media for the capture ofwaterborne or airborne constituents and particles is a media comprisedof a granular substrate and a mixture of amphoteric compounds,preferentially from oxides of aluminum, manganese, iron or siliconbonded to granular substrates in the absence of a crystal inhibitingagent. The solution mixtures are binary mixtures, examples of which areiron and manganese, aluminum and manganese, iron and aluminum or siliconin combination with either, iron, manganese or aluminum. The proportionsof the selected oxides may be dependent, in part, on the surface charge,net point of zero charge (pzc), and the relative population of chargedsites (both positive and negative) created by the resulting mineralcoating at a given pH, in order to target a specific constituent orcompetitive combination of constituents. Solution mixtures do not haveto be only binary. For example, manganese can be added to a binarymixture of iron and aluminum to create a lower net pzc and create arelative increase of negatively charged sites allowing the treatment ofboth positively and negatively charged constituents. One of ordinaryskill in the art will recognize that differing ratios of these oxideswill result in coatings with a range of differing sorptive-filtrationproperties and these variable affinities would be altered by designdepending on the competitive combination of constituents, aqueouschemistry (for example pH), hydrodynamics, equilibrium capacity andkinetics of the particular situation.

5. Embodiment 1 Through 4 Having a Specific Gravity Between 0.2 and 1.0

Another embodiment of the present invention includes asorptive-filtration media which comprises a substrate as described inembodiment 1 through 4 and having a specific gravity betweenapproximately 0.2 and 1.0.

6. Embodiment 1 Through 4 Having a Specific Gravity Between 1.0 and 6.0

Another embodiment of the present invention includes asorptive-filtration media as described in embodiment 1 through 4 andhaving a specific gravity between approximately 1.0 and 6.0.

7. Embodiment 1 Through 4 Composed of Rock, Earthen or Modified-EarthenSubstrate

Another embodiment of the present invention includes asorptive-filtration media which comprises a substrate of rock, nativeearthen material; such as clay, silt, sand, volcanic material,biological materials such as shells or modified earthen material (forexample to create a specific size gradation, altered surface area orbulk density) such as perlite, fired silt or clay particles or rubble,cemented soil material, volcanic material (such as pumice), orcalcareous material.

8. Embodiment 1 Through 4 Composed of a Cementitious Substrate

Another embodiment of the present invention includes asorptive-filtration media which comprises a substrate of cementitiousmaterial such as created with a Portland cement, lime-cement,combination of calcium-alumina-silica, or a material with pozzolanicattributes; where a pozzolan is a siliceous or siliceous and aluminousmaterial that possesses little or no bonding ability, but when finelyground into a high surface area particles and in the presence ofmoisture will react with calcium hydroxide at ambient temperatures toform resulting compounds that possess cementitious properties.

9. Embodiment 1 Through 4 Composed of Cementitious Substrate andAmphoteric Admixture or Amphoteric Coating

Another embodiment of the present invention includes asorptive-filtration media which comprises a substrate of cementitiousmaterial such as created with a portland cement, lime-cement,combination of calcium-alumina-silica, or a material with pozzolanicattributes combined with an metal oxide or metal salt admixture in thecementitious material. One example of such an embodiment is described.The formulation can be scaled to meet specific media amountrequirements, or altered to fit porosity, bulk density, surface area orsurface charge requirements. This example illustrates an amphotericcoating process for aluminum oxide. However, the coating can becomprised of an oxide of iron, manganese or silicon or a combination ofthese oxides as described above.

1. Mix portland cement and clean water at a water/cement (w/c) ratio ofapproximately 0.3 to 0.7. In one embodiment, the water, containers,mixers, forms, admixtures, air-entraining agents, and cement should befree of contamination from the compounds that are intended to be treatedby the media produced by this method. Keeping such contaminants out ofthe resulting substrate/media is beneficial since the substrate will notbe acid-washed as with other substrates such as clay, silt, sand,polymeric media, etc.2. Add a gas-entraining agent. A gas-entraining (or foaming or blowing)agent can function to lower the dry density of the resultingcementitious matrix towards 50 pounds per cubic foot by creating a verylarge number of very small entrained air bubbles (the conventionalphilosophy for a concrete based on strength and dimensional stability);or function to create larger and fewer pores. This latter function canbe combined with an altered w/c ratio to create a porous cementitiousmatrix of lower density and a pore size distribution (PSD) that canrange from single micron size to millimeter size. The latter function ispreferred because the resulting media is a high surface area materialwith internal media pores that are sufficiently large to result in onemode of hydraulic communication through the media as well as anothermode of hydraulic communication through the pore space between themedia.3. There are many gas-entraining agent (derivatives of organic acids,natural or synthetic resins, detergents, anionic surfactants,sulfonates, etc.) and systems that are available. These agents shouldnot contain significant levels of contaminants that are intended to beremoved by the media and should not produce a toxicity product. Thisembodiment utilizes a permeable cementitious matrix in a differentmanner than in a conventional “impermeable” or “non-perviousapplication. The preferred attributes of one embodiment of thispermeable cementitous media are a non-uniform PSD, open pore structure,lower density, reasonable specimen strength (for example a 28-daycompressive strength, f′_(c) of 50 psi or greater and some resistance toabrasive handling), no contaminants or toxicity residuals and a materialthat carbonates over time converting calcium hydroxide to calciumcarbonate.4. Once water/cement and gas-entraining or similar agent are mixed andthe gas-holding matrix is created, the mix is placed in a mold whosegeometry is based on convenience, curing, handling, later crushing,stacking, etc. For example, thinner slabs will allow greater carbonationof material as compared thicker geometries of less surface area. Thegas-entrained cementitious material is then cured for a minimum of 12hours for ambient air curing. Curing can be steam or pressure curing, orboth, but this is not required.5. Once cured, the material is broken or crushed to a selected mediasize and shape. Broken or crushed media that does not fit the media sizerequirements is discarded or re-used. The media size gradation can rangefrom uniform (approximately one equivalent diameter size) tonon-uniform. Media sizes and size gradations can range from 0.01 to 500mm depending on head loss requirements and sorptive-filter efficiencyrequirements.6. The media is then coated with a minimum concentration of about 0.1-M(or higher depending on coverage requirements) aluminum nitrate. Thiscan be a batch coating process, a dipping process or a spraying process.The porous cementitious material coats well. Once coated, the media isdried at a minimum temperature of 60 C for a minimum of 4 hours todryness and then washed with clean tap water. The dry media is thensacked or placed in cartridges.10. Embodiment 1 Through 9 with Substrate SSA Greater than 0.1 m²/gm

Another embodiment of the present invention includes asorptive-filtration media which comprises a substrate with a specificsurface area (SSA) of greater than 0.1 m²/gm.

11. Embodiment 1 Through 5 with a Polymeric Substrate of SSA Greaterthan 0.03 m²/gm

Another embodiment of the present invention includes asorptive-filtration media which comprises a polymeric substrate with aspecific surface area (SSA) of greater than 0.03 m²/gm.

12. Embodiment 1 Through 5 with a Cemented or Metamorph of Clay or SiltSubstrate

Another embodiment of the present invention includes asorptive-filtration media which comprises a clay or silt substrate thathas been cemented or has undergone metamorphosis through heating and/orpressure and/or chemical modification. Cementing of clay or siltsubstrates to form sorptive-filtration media or aggregates can becarried out with Portland cement, lime or cementing agents that are usedto form larger aggregate media from binding much smaller clay or siltparticles together. Media size ranges can have equivalent diametersbetween 0.01 mm and 500 mm.

13. Embodiment 12 without an Amphoteric Coating

Another embodiment of the present invention includes asorptive-filtration media which comprises a clay or silt substrate thathas been cemented or has undergone metamorphosis through heat and/orpressure and/or chemical modification and no amphoteric coating.

14. Embodiment 1 Through 13 with a Particle Size Range from 0.01 mm to500 mm

Another embodiment of the present invention includes asorptive-filtration media ranging in size from 0.01 mm to 500 mm. Below0.01 mm, hydraulic conductivities are too low for the medium to functioneffectively as a filter at common surface loading rates between 0.1 and10 gallons/ft²-minute and above 500 mm, specific surface area, pore sizeand residence times are too large to have a significant benefit ontreatment for particles or solutes.

15. Embodiment 12 with an Amphoteric Coating.

Another embodiment of the present invention includes asorptive-filtration media which comprises a clay or silt substrate thathas been cemented or has undergone metamorphosis through heat and/orpressure and/or chemical modification with an amphoteric coating. Oneexample of such an embodiment is described. The formulation can bescaled to meet specific media amount requirements, or altered to fitporosity, bulk density, surface area, surface charge requirements orcontaminant sorption requirements. This example illustrates anamphoteric coating of aluminum oxide. However, the coating can becomprised of an oxide of iron, manganese or silicon or a combination ofthese oxides as described above.

1. Mix 2 kg of water at 15 to 35 C with a biological blowing agent. Onepreferred blowing agent is yeast which is added at approximately 1% orgreater by dry weight of total dry clay. There are a variety ofbiological blowing agents that can be added. Depending on the mixingconditions, yeast and temperature, this mixing may require severalminutes or longer. As soon as the mixture begins to froth or bubble withevolved gas, ground clay is added and mixed into the gas-water mixture.As with a cementitious matrix there are many gas-entraining, foaming orblowing agents for a cohesive matrix. In this example, yeast spores areuniformly interspersed in the clay matrix, coming out of a spore-phasebecause of the water, temperature and nutrients, to produce copiousamounts of gas bubbles. Organic and inorganic chemical blowing agents orphase-changing blowing agents can also be utilized. Physical blowingagents can also be utilized and have shown success. One of the benefitsof yeast is that the there is little residual agent left after firing.2. Mix or blend in 1 kg of ground kaolinite (a common clay mineral) intothe 2 kg of water3. After the kaolinite is blended in, mix rapidly in about ⅓ of 0.5 kgof sodium bentonite (main ingredient in drilling mud, sealing mud,slurry mud), trapping and coalescing the gas bubbles. Allow the viscousclay to set for a minute or longer. A very lumpy texture will begin toform. After several minutes mix in the balance of the bentonite. Put inmolds where in this case, clay slurry depth is important. Clay slurrydepth in the molds should be at least 1 inch deep. Allow the clay toremain in the molds for 30 minutes or longer at a temperature of atleast 15 C before placing in an oven at 60 C for at least 2 hours. Oneof ordinary skill in the art will recognize that there are manyvariations of this formulation that will provide differing mediaporosities and bulk densities depending on media requirements.4. After drying with sufficient moisture driven off fire the clay at aminimum temperature of 500 C for at least 1 hour or longer. After thefiring, allow to cool and the crush or break to same specifications asembodiment 14.5. Soak media in a 0.1-M or greater nitric acid solution for 30 minutesto remove any residual contaminants that are part of the clay, water,molds or agents. Rinse off acid from media surface with clean water. Ifthere are no contaminants or trace levels of contaminants this step isnot required.6. The media is then coated with a minimum concentration of 0.1-M (orhigher depending on coverage requirements) aluminum nitrate. This can bea batch coating process, a dipping process or a spraying process. Theporous clay material coats very well because of high surface area andsurface charge. Once coated, the media is dried at 60 C for at least 4hours to dryness and then washed with clean water. The dry media is thensacked or placed in cartridges. The resulting media is very porous,hydroscopic, with a very porous and a rough surface for filtration andhas a good compressive strength (cannot be crushed by hand) and is notfriable. The media can have significant internal pore structure.16. Embodiment 1 Through 14 with an Amphoteric Admixture

Another embodiment of the present invention includes asorptive-filtration media which comprises a clay or silt substrate thathas been cemented or has undergone metamorphosis through heat and/orpressure and/or chemical modification with an amphoteric substanceadmixture.

17. Embodiment 1 Through 14 with an Amphoteric Admixture and Coating

Another embodiment of the present invention includes asorptive-filtration media which comprises a clay or silt substrate thathas been cemented or has undergone metamorphosis through heat and/orpressure and/or chemical modification with an amphoteric admixture and afurther amphoteric coating.

18. A Porous Pavement Medium with a Single Oxide Amphoteric Coating

One embodiment of the present invention is a pavement medium materialfor the capture of waterborne constituents including particles. Thepavement material comprises a porous pavement substrate and a singleamphoteric compound, preferentially an oxide of aluminum, manganese,iron or silicon applied to the porous pavement medium substrate ineither the absence or presence of a crystal inhibiting agent.

19. A Porous Pavement Medium, with Amphoteric Coating of Mixed Oxides

Another embodiment of the present invention is a pavement mediummaterial for the capture of waterborne constituents including particles.The pavement material comprises a porous pavement substrate and amixture of amphoteric compounds, preferentially from oxides of aluminum,manganese, iron or silicon applied to the porous pavement mediumsubstrate in the absence or presence of a crystal inhibiting agent.

20. A Porous Pavement Medium, with Admixture in Binder

Another embodiment of the present invention is a pavement mediummaterial for the capture of waterborne constituents including particles.The pavement material comprises a porous pavement substrate matrix madefrom a binder wherein the water fraction of this binder is comprised inpart of an aqueous solution of an amphoteric metal oxide or saltadmixture.

21. A Cementitious Porous Pavement Medium, with w/c Admixture

Another embodiment of the present invention is a pavement mediummaterial for the capture of waterborne constituents including particles.The cementitious pavement material comprises a porous pavement substratematrix made from a water:cement ratio and an amphoteric compound orcombinations of aluminum, manganese, iron and silicon compounds utilizedas part of the water:cement ratio. In this embodiment, the pavementsubstrate is also comprised of fine and/or coarse aggregate.

22. A Porous Pavement Medium, with Full-Depth Layered AmphotericCoatings

Another embodiment of the present invention is a pavement mediummaterial for the capture of waterborne constituents including particles.The pavement material comprises a porous pavement substrate withseparate horizontal coating layers of amphoteric compounds,preferentially from oxides of aluminum, manganese, iron or silicon,applied to the porous pavement medium substrate in the absence orpresence of a crystal inhibiting agent.

23. A Porous Pavement Medium, with Partial-Depth Layered AmphotericCoatings

Another embodiment of the present invention is a pavement mediummaterial for the capture of waterborne constituents including particles.The pavement material comprises a porous pavement substrate withseparate horizontal coating layers of amphoteric compounds,preferentially from oxides of aluminum, manganese, iron or silicon,applied to the porous pavement medium substrate in the absence orpresence of a crystal inhibiting agent. In one variation of thisembodiment, the upper 20% or less of the pavement remains uncoated.

24. A Porous Pavement Medium, with Full-Depth Mixture of AmphotericCoatings

Another embodiment of the present invention is a pavement mediummaterial for the capture of waterborne constituents including particles.The pavement material comprises a porous pavement substrate and amixture of amphoteric compounds, preferentially from oxides of aluminum,manganese, iron or silicon applied to the porous pavement mediumsubstrate in the absence or presence of a crystal inhibiting agent. Inthis embodiment the full depth of the pavement is coated with a mixtureof amphoteric coatings.

25. A Layered Porous Pavement Medium, with Partial-Depth LayeredAmphoteric Coatings

Another embodiment of the present invention is a pavement mediummaterial for the capture of waterborne constituents including particles.The pavement material comprises a porous pavement substrate withseparate pavement material layers. In this embodiment one or more layerswill not be applied with an amphoteric compound while one or more otherlayers will be applied with one or a mixture of amphoteric compounds,preferentially from oxides of aluminum, manganese, iron or silicon,applied to the porous pavement medium substrate in the absence orpresence of a crystal inhibiting agent.

26. A 3″Porous Pavement Medium, with a Full-Depth of Amphoteric Coating

Another embodiment of the present invention is a pavement mediummaterial for the capture of waterborne constituents including particles.The pavement material comprises a porous pavement substrate and anamphoteric compound or a mixture of amphoteric compounds, preferentiallyfrom oxides of aluminum, manganese, iron or silicon applied to theporous pavement medium substrate in the absence or presence of a crystalinhibiting agent. In this embodiment the full depth of the pavement iscoated with an amphoteric compound or mixture of amphoteric compoundsand the pavement depth is at least 3 inches.

27. A 3″Porous Pavement Medium, with a Partial-Depth Amphoteric Coating

Another embodiment of the present invention is a pavement mediummaterial for the capture of waterborne constituents including particles.The pavement material comprises a porous pavement substrate and anamphoteric compound or mixture of compounds preferentially from oxidesof aluminum, manganese, iron or silicon applied to the porous pavementmedium substrate in the absence or presence of a crystal inhibitingagent. In this embodiment the upper 20% of the pavement is not coatedwith an amphoteric coating and the pavement depth is at least 3 inches.

28. A 3″ or deeper porous pavement storage basin

A further embodiment includes a runoff or drainage storage orstorage/treatment basin capable of supporting vehicular traffic. Thebasin comprises a layer of porous pavement having a hydraulicconductivity of more than 0.0001 cm/sec. The layer of porous pavement isat least 3 inches in depth, and the layer has a length and a widthwherein the ratio between the length and the width is less than 50. Thetotal porosity of the porous pavement is greater than 0.10. The pavementmay comprise a compressive strength of at least about 2000, 3000, or4000 psi in other embodiments.

29. A 3″ or Deeper Porous Pavement Storage Basin w/an Embodiment from 15Through 24

A further embodiment includes a runoff or drainage storage orstorage/treatment basin capable of supporting vehicular traffic. Thebasin comprises a layer of porous pavement having a hydraulicconductivity of more than 0.0001 cm/sec. The layer of porous pavement isat least 3 inches in depth, and the layer has a length and a widthwherein the ratio between the length and the width is less than 50. Thetotal porosity of the porous pavement is greater than 0.10.

30. Process; Substrate SSA >0.1 m²/gm and Amphoteric Coating fromImmersion

One embodiment includes a process for producing a sorptive-filtrationmedia for the capture of waterborne or airborne constituents andparticulates. The process comprises the steps of providing a substratehaving a specific surface area (SSA) of greater than 0.1 m²/gm,introducing the substrate to a solution (through mixing and partialimmersion) such as a metal salt or oxide solution, of one or acombination of aluminum, manganese, iron and silicon compounds andvolatilizing or drying the solution, leaving a coating on the substrate(including inside the outer surface of the substrate for poroussubstrates). This resulting coated substrate has amphoteric propertiesin aqueous solution.

31. Process; Substrate SSA >0.1 m²/gm and Amphoteric Coating fromSpraying

Another embodiment includes a process for producing asorptive-filtration media for the capture of waterborne or airborneconstituents and particulates. The process comprises the steps ofproviding a substrate having a specific surface area (SSA) of greaterthan 0.1 m²/gm, introducing the substrate to a solution such as a metalsalt or oxide solution, of one or a combination of aluminum, manganese,iron and silicon compounds by spraying the solution onto the substrateor passing the substrate through a spray, and volatilizing or drying thesolution, leaving a coating on the substrate (including inside the outersurface of the substrate for porous substrates). This resulting coatedsubstrate has amphoteric properties in aqueous solution.

32. Process; Cementitious Coating with Admixture

Another embodiment includes a process for producing asorptive-filtration media for the capture of waterborne or airborneconstituents and particulates. The process comprises the steps ofcoating a substrate with a cementitious coating wherein the aqueousfraction of the water:cement ratio includes a solution of one or acombination of aluminum, manganese, iron and silica oxide or saltcompounds. This coating with an admixture is dried on the substrate withor without the benefit of drying aids such as additional temperature,enhanced vapor gradients or convective gradients.

33. Process; Cementitious coating with amphoteric coating

Another embodiment includes a process for producing asorptive-filtration media for the capture of waterborne or airborneconstituents and particulates. The process comprises the steps ofcoating a substrate with a cementitious coating. This coating is driedon the substrate with or without the benefit of drying aids such asadditional temperature, enhanced vapor gradients or convectivegradients. The cementitious coated substrate is contacted with asolution of metal salt or oxide solution, of one or a combination ofaluminum, manganese, iron and silicon compounds. The contact method iseither through mixing, immersion or spraying. The coating of metal saltor oxide solution on the surface is volatilized or dried, leaving acoating on (and within) the cementitious coating.

34. Process; Cementitious media with admixture

Another embodiment includes a process for producing asorptive-filtration media for the capture of waterborne or airborneconstituents and particulates. The process comprises the steps ofcreating a substrate from cement and an aqueous solution where theaqueous solution is comprised, in part, of solution of one or acombination of aluminum, manganese, iron and silica oxide or saltcompound. The substrate slurry, paste or mixture is cured, and formed ormade into granular media of a chosen size gradation and functions as asorptive-filtration media.

35. Process; Cementitious Media Containing Aggregate with Admixture

Another embodiment includes a process for producing asorptive-filtration media for the capture of waterborne or airborneconstituents and particulates. The process comprises the steps ofcreating a substrate from cement, fine or coarse aggregate, and anaqueous solution including a solution of one or a combination ofaluminum, manganese, iron and silica oxide or salt compound. Thesubstrate slurry, paste or mixture is cured and formed or made intogranular media of a chosen size gradation and functions as asorptive-filtration media.

36. Process; Cementitious Media w/Aggregate, w/Admixture and AmphotericCoating

Another embodiment includes a process for producing asorptive-filtration media for the capture of waterborne or airborneconstituents and particulates. The process comprises the steps ofcreating a substrate from cement and an aqueous solution where theaqueous solution includes a first solution of one or a combination ofaluminum, manganese, iron and silica oxide or salt compound. Thesubstrate can be created with or without fine or coarse aggregate. Thesubstrate slurry, paste or mixture is cured and formed or made intogranular media of a chosen size gradation and functions as asorptive-filtration media. The resulting sorptive-filtration substrateis introduced to a second solution (by mixing, immersion or spraying)such as a solution of one or a combination of aluminum, manganese, ironand silica oxide or salt compound (which may be the same as or differentfrom the first solution), and volatilizing or drying the solution,leaving a coating on the substrate (or inside the outer surface of thesubstrate for porous substrates). This resulting coated substrate is asorptive-filtration media.

37. Embodiment 30 Through 36 Resulting in Media with Specific GravityBetween 0.2 and 1.0

Another embodiment is a sorptive-filtration media formed through aprocess of providing a granular media with a specific gravity betweenabout 0.1 and about 0.9 and applying to said granular media anamphoteric cementitious substance formed by any method, includingembodiments 30-36, in a full or partial coating of said media. Incertain embodiments, the thickness of the coating will be such that thetotal specific gravity of the coated media will be less than 1. In theseembodiments, lower composite specific gravities will require thinnercoatings, down to about 50 microns, whereas higher specific gravities(up to 1) can be achieved with thicker coatings (depending in thedensity of the substrate) of up to about 1 mm

38. Embodiment 30 Through 36 Resulting in Media with Specific GravityBetween 1.0 and 6.0

Another embodiment is a sorptive-filtration media formed through aprocess of providing a granular media with a specific gravity betweenabout 1.0 and about 6.0 and applying to said granular media anamphoteric cementitious substance formed by any method, includingembodiments 30-36, in a full or partial coating of said media. Anotherembodiment employs a media having a specific gravity of between about2.4 and about 0.3 (non-limiting examples of which are perlite andpumice). This latter embodiment could have a size range from about 0.5mm to about 100 mm. The specific gravity of perlite is 2.2 to 2.4, butthe bulk density of perlite is much lower (about 0.4 to 0.8) since it isfilled with voids. The specific gravity of pumice is 0.6 to 0.7 and thebulk density is about 0.4 to 0.6. One size range for this material thatis suitable for filtration is about 0.8 mm to 10 mm

39. Process, Production of CPP with w/c<1 without AmphotericCoating/Admixture

Another embodiment includes a method for producing a porous,cementitious material. The method includes the steps of providing andthoroughly mixing cement and fine and/or coarse aggregate, mixing waterwith the cement and aggregate into a slurry while maintaining a water tocement ratio of less than one, initiating curing of the slurry underpressure and in the presence of steam, and continuing the curing atambient temperature and pressure until the cementitious material issubstantially dry. Another embodiment of this is to carry out curing atambient pressure, temperature and humidity. The total porosity of theporous pavement is greater than 0.05.

40. Process, Production of CPP with w/c<1 and with AmphotericCoating/Admixture

Another embodiment includes a method for producing a porous,cementitious material. The method includes the steps of providing andthoroughly mixing cement and aggregate, mixing an aqueous solutioncomprised of one or a combination of aluminum, manganese, iron andsilicon oxide or salt compounds with the cement and aggregate into aslurry while maintaining the water (aqueous solution) to cement ratio ofless than one, initiating curing of the slurry under pressure and in thepresence of steam, and continuing the curing at ambient temperature andpressure until the cementitious material is substantially dry. Anotherembodiment of this is to carry out curing at ambient pressure,temperature and humidity. The total porosity of the porous pavement isgreater than 0.05. In each embodiment 39-41, those embodiments couldalso be produced with a water to cement ratios of less than 0.9, lessthan 0.8, less than 0.7, less than 0.6, less than 0.5, or less than 0.4,less than 0.3, less than 0.25, or less than 0.15 (if cured in thepresence of steam)

41. Process, Production of CPP without Steam, with w/c<1 and Embodiment35 and 36

Another embodiment includes a method for producing a porous,cementitious material. The method includes the steps of providing andthoroughly mixing cement and aggregate, mixing an aqueous solutioncomprised of one or a combination of aluminum, manganese, iron andsilicon oxide or salt compounds with the cement and aggregate into aslurry while maintaining the water (aqueous solution) to cement ratio ofless than one, initiating curing of the slurry under atmosphericpressure and continuing the curing at ambient temperature and pressureuntil the cementitious material is substantially dry. The total porosityof the porous pavement is greater than 0.05. This embodiment can also beproduced without an amphoteric compound.

42. Aggregate for Shoulder Coated with Amphoteric Compound

Another embodiment is a roadway or pavement system with a shoulderformed of a cementitious granular material (e.g. aggregate formed ofcrushed concrete) for the removal of waterborne dissolved ionic,complexed or particulate-bound constituents. The roadway or pavementsystem comprises a pavement section and a gravel shoulder sectionadjacent to the pavement section. The sand to very coarse gravel-sizematerial has a depth of at least 3 inches and includes sand, gravel,crushed or rubble material coated by an amphoteric compound of aluminum,manganese, iron and silicon or combination thereof.

43. Cementitious Aggregate for Shoulder Coated with Amphoteric Compound

Another embodiment is a roadway or pavement system with a cementitiousgranular shoulder for the removal of waterborne dissolved ionic,complexed or particulate-bound constituents. The roadway or pavementsystem comprises a pavement section and a cementitious granular shouldersection adjacent to the pavement section. The cementitious granularshoulder has a depth of at least 3 inches and includes cementitiousgranular or crushed cementitious, aggregate or rubble material coated byan amphoteric compound of aluminum, manganese, iron and silicon orcombination thereof.

44. Cementitious Aggregate for Shoulder with an Admixture of AmphotericCompound

Another embodiment is a roadway or pavement system with a cementitiousgranular shoulder for the removal of waterborne dissolved ionic,complexed or particulate-bound constituents. The roadway or pavementsystem comprises a pavement section and a cementitious granular shouldersection adjacent to the pavement section. The cementitious granularshoulder has a depth of at least 3 inches and includes cementitiousgranular or crushed cementitious, aggregate or rubble material made withan admixture of amphoteric compound of aluminum, manganese, iron andsilicon or combination thereof.

45. Amphoteric Sub-Base or Base Material

Another embodiment includes a method of constructing a sub-base or basesubgrade for the removal of waterborne constituents. The method includesthe steps of placing a layer of uncompacted sub-base or base material;distributing upon the layer or mixing in the layer a solution containingan amphoteric compound of aluminum, manganese, iron and silica oxide orsalt, or combination thereof, and compacting or densifying the layer toa selected density.

46. Amphoteric Sub-Base or Base Material with Cementitious Admixture

Another embodiment includes a method of constructing a sub-base or basesubgrade for the removal of waterborne constituents. The method includesthe steps of placing a layer of uncompacted sub-base or base material;distributing upon the layer or mixing in the layer a solution or slurrycontaining cement, lime or pozzolanic material and amphoteric compoundof aluminum, manganese, iron and silica oxide or salt, or combinationthereof, mixing in and compacting or densifying the layer to a selecteddensity.

47. Amphoteric Sub-Base or Base Material with Cementitious Admixture

Another embodiment is a sorptive-filtration medium for the capture ofwaterborne or airborne constituents. The media comprises a flexible,thin (less than 30 cm), planar, porous substrate such as a synthetic ornatural geotextile, geosynthetic or geocomposite substrate material; andan amphoteric compound of aluminum, manganese, iron and silica oxide orsalt applied to the substrate.

48. 3-D Flexible Porous, Hydraulically-Conductive Medium with AmphotericCoating

Another embodiment is an sorptive-filtration medium for the capture ofwaterborne or airborne constituents. The medium comprises a flexible,3-dimensional, hydraulically-conductive porous substrate matrix; and anamphoteric compound or combination of aluminum, manganese, iron andsilicon oxide or salt applied to the substrate matrix. In thisapplication, hydraulically-conductive relates to the ability of themedium to conduct liquid or gas through the medium. The medium is aplanar medium that has a thickness of greater than 1 mm. This medium canbe formed into irregular or regular geometries and is deformable yetpossesses sufficient strength to retain a pre-determined shape underit's own weight or without peripheral containment required to retain apre-determined shape. Non-limiting examples of such hydraulicallyconductive matrix include porous foams, woven and non-wovengeosynthetics, or mats of natural fiber materials.

49. 3-D Flexible Porous Polymeric Medium with Amphoteric Coating

Another embodiment is a sorptive-filtration medium for the capture ofwaterborne or airborne constituents. The media comprises a flexible,3-dimensional, porous natural or polymeric substrate such as ageosynthetic; and an amphoteric compound or combination of aluminum,manganese, iron and silica oxide or salt applied to the substrate.

50. 3-D Flexible Porous Medium (as in Embodiment 48 and 49) withCementitious Coating

Another embodiment is a sorptive-filtration medium for the capture ofwaterborne or airborne constituents. The media comprises a flexible,3-dimensional, porous natural or polymeric substrate such as ageosynthetic; and a cementitious coating with either an admixturecontaining an amphoteric compound or combination of aluminum, manganese,iron and silica oxide or salt, or a coating of the compound(s).

51. Drainage Pipe or Fixture with Amphoteric Coating

Another embodiment is a drainage pipe, hydraulic system or fixturecapable of capturing waterborne or airborne constituents. The pipe,system, conveyance structure or fixture has an an interior surface, atleast a portion of the surface being designed to be in contact withwater or gas. One example is a pipe sewer. An amphoteric compound orcombination of compounds is then applied to the portion of the surfacedesigned to be in contact with the fluid.

52. Media or Medium with Multiple Layers of Amphoteric Coatings

Another embodiment of the invention includes a process for creating asorptive-filtration media or medium for the capture of waterborne orairborne constituents. The process comprises the steps of providing asubstrate (inorganic, organic, cementitious, earthen, rock,non-cementitious, pozzolonic) and applying a first coating of an oxidecompound to the substrate; and applying a second coating of anotheroxide compound to the first coating. This coating process can continuefor “n” layers of differing or similar oxide coatings.

53. Media or Medium with Cementitious Coating and Multiple Layers ofAmphoteric Coatings

Another embodiment of the invention includes a process for creating asorptive-filtration media or medium for the capture of waterborne orairborne constituents. The process comprises the steps of providing asubstrate (inorganic, organic, cementitious, earthen, rock,non-cementitious, pozzolonic), applying a cementitious layer to dryness,and then applying a first coating of an oxide compound to the substrate;and applying a second coating of another oxide compound to the firstcoating. This coating process can continue for “n” layers of differingor similar oxide coatings.

54. Shoulder with Amphoteric Admixture/Coatings

Another embodiment of the invention includes a roadway with a shoulderor any paved area forming a filter for dissolved ionic, complexed orparticulate-bound species. The roadway or paved area comprises a pavedsection such as a traveled pavement and a cementitious, porous, shoulderadjacent the paved section and the shoulder having an amphotericcompound or combination of amphoteric compounds applied thereto, oradmixture thereof as part of the water:cement ratio. The total porosityranges from approximately 0.05 to 0.6.

55. Paved Porous Area with Amphoteric Admixture/Coatings

Another embodiment of the invention includes any paved area forming afilter for dissolved ionic, complexed or particulate-bound species. Thepaved area is comprised of cementitious, porous material having anamphoteric compound or combination of amphoteric compounds applied orbonded thereto, or admixture thereof as part of the water:cement ratio.The total porosity ranges from approximately 0.05 to 0.6.

56. Porous Media with Amphoteric Admixture/Coatings

Another embodiment provides a sorptive-filtration media having a porousstructure of a fixed matrix and a total porosity of approximately 0.05to 0.6 and an amphoteric compound or combination of amphoteric compoundsapplied thereto or as an admixture thereof.

57. Porous Pavement with or without Amphoteric Admixture/Coatings

Another embodiment includes a method for forming a porous pavementroadway. This method includes the steps of providing and thoroughlymixing cement and aggregate; mixing water with the cement and aggregateforming it into a slurry while maintaining a water to cement ratio ofless than one; and placing the slurry into a roadway bed. The totalporosity ranges from approximately 0.05 to 0.6. The water:cement ratiocan be made with or without an amphoteric compound or combination ofaluminum, manganese, iron and silica oxide or salt.

Applications of the above embodiments include without limitationpavement systems, media systems, clarifiers, filters, hydrodynamicsystems, transportation systems. Other embodiments include in-situsystems such as in-situ partial exfiltration systems where the containermay be a synthetic polymeric or natural material such as a geosyntheticserving as the containing interface between the media and thesurrounding soil environment. Still further non-limiting applicationsinclude inlets or catch-basins for storm water, wastewater, naturalflows or anthropogenic flows such as industrial flows, end of conduitdischarges, hydrodynamic or volumetric separation systems, directeddischarges from elevated infrastructure such as downspouts, buildingdrains or bridge drainage, or as inserts in or appurtenances to unitoperations and processes (UOPs). Specific embodiments of this lastapplication include in-line or off-line adsorptive-filtration ofdischarges from these UOPs, for example treatment of discharges from abasin or clarifier that might provide preliminary or primary treatment,application of the sorption-filtration media or fixed medium as a directprimary treatment, or inclusion of the sorptive-filtration media withinall or part of the volume of a unit operation or process (sometimescalled best management practices, BMPs). Ex-situ applications before orafter UOPs can include cartridge or tubular filters or fluidized bedsystems.

These in-situ or ex-situ media embodiments can be arranged in series;for example layers of media of differing size, differing coating,differing substrates, differing pzc or charge, differing specificgravity, differing conductivities, or differing substrates in a singlefixed or flexible container or in separate fixed or flexible containerssuch as cartridges, tubes, compartments or zones. These in-situ orex-situ medium embodiments such as cementitious porous pavement or3-dimensional porous materials can also be arranged in series havingdiffering characteristics. The relative proportion of these series willdepend on the treatment performance desired for specific constituents(for examples metals or phosphorus) and for specific particlegradations. These in-situ or ex-situ embodiments can be arranged inseries and include a process for producing a sorptive-filtration mediafor the capture of waterborne or airborne constituents and particulates.The process comprises the steps of providing a substrate with a specificsurface area of greater than 0.1 m²/gm, introducing the substrate to asolution such as a metal salt solution, of one or a combination ofaluminum, manganese, iron and silicon compounds and volatilizing thesolution, leaving a coating on the substrate (or inside the outersurface of the substrate for porous substrates). This resulting coatedsubstrate has amphoteric properties in aqueous solution. All of thesevariations are intended to come within the scope of the followingclaims.

1. A sorptive-filtration system for removing at least one of negativelyor positively charged ions, complexes or particulates from an aqueousstream, comprising: a. flow formed substantially from at least one ofrainfall-runoff or snowmelt-runoff; b. a filter containmentcommunicating with said flow such that at least part of said flow passesthrough said filter containment; and c. a granular filter media disposedwithin said filter containment, said filter media comprising anamphoteric material applied thereto, wherein said amphoteric materialcomprises a metal selected from at least one of Al, Mn, or Si.
 2. Thefiltration system of claim 1, wherein said amphoteric material is atleast one oxide of a metal selected from at least one of Al, Mn, or Si.3. The filtration system of claim 1, wherein said filter media is agranular media having a porosity of between about 0.2 and about 0.7. 4.The filtration system of claim 1, wherein said amphoteric materialcomprises both an oxide of Si and at least one oxide of a metal selectedfrom at least one of Al, Mn, or Fe.
 5. The filtration system of claim 4,wherein said filter media comprises a first media having a Si oxideapplied thereto and a second media having at least one oxide of at leastone of Al, Mn, or Fe.
 6. The filtration system of claim 1, wherein saidfilter containment is formed by a porous textile or geotextile material.7. The filtration system of claim 1, wherein said filter containment isformed by a porous mesh material.
 8. The filtration system of claim 7wherein said porous mesh material is a wire mesh.
 9. The filtrationsystem of claim 1, wherein said filter system includes a rigid mediahousing and said filter containment is a flexible material generallyshaped to fit within said media housing.
 10. The filtration system ofclaim 3, wherein said filter media is a granular media having ahydraulic conductivity of between about 1.0 and about 0.0001 cm/sec. 11.The filtration system of claim 1, wherein said media has a specificgravity of between about 0.2 and about 1.0.
 12. The filtration system ofclaim 1, wherein said media has a specific gravity of between about 0.2and about 1.0.
 13. The filtration system of claim 1, wherein said mediacomprises a granular substrate having an average diameter ranging from0.1 mm to 100 mm.
 14. The filtration system of claim 1, wherein saidgranular media is produced by a process comprising the steps of: a.providing said granular media; b. applying an amphoteric solution tosaid media; c. drying said media to leave an amphoteric coating thereon.15. The filtration system of claim 14, wherein said step of applyingsaid amphoteric solution is accomplished by at least one of: i)immersing said media in said amphoteric solution; ii) spraying saidamphoteric solution onto said media; or iii) adding an amphotericsolution to a precursor of said media.
 16. The filtration system ofclaim 1, wherein said media is a granular media produced by a processcomprising the steps of: a. providing said granular media; b. providinga wet cement mix comprising in part an amphoteric solution; c. coatingsaid media with said wet cement mix; and d. hydrating or drying said wetcement mix on said substrate.
 17. The filtration system of claim 16,wherein said media has a specific gravity of between about 0.2 and about1.0
 18. The filtration system of claim 16, wherein said media has aspecific gravity of between about 1.0 and about 2.4.
 19. The filtrationsystem of claim 1, wherein said granular media is produced by a processcomprising the steps of: a. providing said granular media substrate; b.coating said media with a wet cement mix; c. drying said wet cement mixon said substrate; and d. applying an amphoteric solution to said cementcoated substrate.
 20. The filtration system of claim 1, wherein saidgranular media is produced by a process comprising the steps of: a.providing a wet cement mix comprising in part an amphoteric solution; b.drying said wet cement mix; and c. reducing said dried cement mix intogranular form ranging from about 0.01 mm to about 500 mm in averagediameter.